Transparency, ASP.NET, and GDI+

[Nathan Sokalski]

I am trying to create graphics with GDI+ that include transparency. However,
the transparency never seems to show up, even though my colors have an alpha
value of 0. How can I generate a graphic that is completely transparent in
certain areas (so that the web page background shows through)? I save my
graphics as gif files. I would appreciate, if possible, a simple example so
that I can see the code. Thanks.
--
Nathan Sokalski
njsokalski@hotm ail.com

http://www.nathansokalski.com/

[Kevin Spencer]

Re: Transparency, ASP.NET, and GDI+

The only graphics formats that have transparency in HTML are GIF and PNG.
What format are you using?

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
Everybody picks their nose,
But some people are better at hiding it.

"Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...[color=blue]
>I am trying to create graphics with GDI+ that include transparency.
>However, the transparency never seems to show up, even though my colors
>have an alpha value of 0. How can I generate a graphic that is completely
>transparent in certain areas (so that the web page background shows
>through)? I save my graphics as gif files. I would appreciate, if possible,
>a simple example so that I can see the code. Thanks.
> --
> Nathan Sokalski
> njsokalski@hotm ail.com
> http://www.nathansokalski.com/
>[/color]

[Nathan Sokalski]

Re: Transparency, ASP.NET, and GDI+

Like I said in my original message, I am using GIF. The line that I use to
save my image is as follows (testbitmap is the name of my
System.Drawing. Bitmap object):

testbitmap.Save (Server.MapPath ("GDItest.gif") , Imaging.ImageFo rmat.Gif)

--
Nathan Sokalski
njsokalski@hotm ail.com

http://www.nathansokalski.com/

"Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...[color=blue]
> The only graphics formats that have transparency in HTML are GIF and PNG.
> What format are you using?
>
> --
> HTH,
>
> Kevin Spencer
> Microsoft MVP
> .Net Developer
> Everybody picks their nose,
> But some people are better at hiding it.
>
> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...[color=green]
>>I am trying to create graphics with GDI+ that include transparency.
>>However, the transparency never seems to show up, even though my colors
>>have an alpha value of 0. How can I generate a graphic that is completely
>>transparent in certain areas (so that the web page background shows
>>through)? I save my graphics as gif files. I would appreciate, if
>>possible, a simple example so that I can see the code. Thanks.
>> --
>> Nathan Sokalski
>> njsokalski@hotm ail.com
>> http://www.nathansokalski.com/
>>[/color]
>
>[/color]

[Lloyd Dupont]

Re: Transparency, ASP.NET, and GDI+

I think IE don't support transparency.
At least I can say for sure it doesn't support PNG transparency.
It is an issue that should be fixed with IE 7 or could be fixd with Firefox!

"Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
news:On0xnMtnFH A.2916@TK2MSFTN GP14.phx.gbl...[color=blue]
> Like I said in my original message, I am using GIF. The line that I use to
> save my image is as follows (testbitmap is the name of my
> System.Drawing. Bitmap object):
>
> testbitmap.Save (Server.MapPath ("GDItest.gif") , Imaging.ImageFo rmat.Gif)
>
> --
> Nathan Sokalski
> njsokalski@hotm ail.com
> http://www.nathansokalski.com/
>
> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
> news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...[color=green]
>> The only graphics formats that have transparency in HTML are GIF and PNG.
>> What format are you using?
>>
>> --
>> HTH,
>>
>> Kevin Spencer
>> Microsoft MVP
>> .Net Developer
>> Everybody picks their nose,
>> But some people are better at hiding it.
>>
>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...[color=darkred]
>>>I am trying to create graphics with GDI+ that include transparency.
>>>However, the transparency never seems to show up, even though my colors
>>>have an alpha value of 0. How can I generate a graphic that is completely
>>>transparen t in certain areas (so that the web page background shows
>>>through)? I save my graphics as gif files. I would appreciate, if
>>>possible, a simple example so that I can see the code. Thanks.
>>> --
>>> Nathan Sokalski
>>> njsokalski@hotm ail.com
>>> http://www.nathansokalski.com/
>>>[/color]
>>
>>[/color]
>
>[/color]

[Nathan Sokalski]

Re: Transparency, ASP.NET, and GDI+

I know for sure that IE correctly supports transparency in GIF files because
I have made transparent GIF files using Adobe Photoshop in the past that
worked correctly in IE. What the problem appears to be to me, although I
could be wrong, is that when a new System.Drawing. Bitmap is created in
ASP.NET it automatically gives it a background with an Alpha value of 255
(completely opaque). Because of this, whenever anything is drawn on the
bitmap, it is drawn on top of the opaque background. This means that
anything with an Alpha value of 0 (completely transparent) is not visible.
If this is the case, I think the only solution would be to "erase"
previously drawn pixels (which I do not know of a way to do), including the
background or to have the initial background color have an Alpha value of 0.
This is only a theory, so I could be wrong. A workaround that I have come up
with (but it requires the developer to create an extra file) is to use an
existing image file that is completely transparent in the
System.Drawing. Bitmap constructor. Let me know if you come up with any
ideas. Thanks.
--
Nathan Sokalski
njsokalski@hotm ail.com

http://www.nathansokalski.com/

"Lloyd Dupont" <net.galador@ld > wrote in message
news:eyb0iUunFH A.3120@TK2MSFTN GP09.phx.gbl...[color=blue]
>I think IE don't support transparency.
> At least I can say for sure it doesn't support PNG transparency.
> It is an issue that should be fixed with IE 7 or could be fixd with
> Firefox!
>
> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
> news:On0xnMtnFH A.2916@TK2MSFTN GP14.phx.gbl...[color=green]
>> Like I said in my original message, I am using GIF. The line that I use
>> to save my image is as follows (testbitmap is the name of my
>> System.Drawing. Bitmap object):
>>
>> testbitmap.Save (Server.MapPath ("GDItest.gif") , Imaging.ImageFo rmat.Gif)
>>
>> --
>> Nathan Sokalski
>> njsokalski@hotm ail.com
>> http://www.nathansokalski.com/
>>
>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>> news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...[color=darkred]
>>> The only graphics formats that have transparency in HTML are GIF and
>>> PNG. What format are you using?
>>>
>>> --
>>> HTH,
>>>
>>> Kevin Spencer
>>> Microsoft MVP
>>> .Net Developer
>>> Everybody picks their nose,
>>> But some people are better at hiding it.
>>>
>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>I am trying to create graphics with GDI+ that include transparency.
>>>>However, the transparency never seems to show up, even though my colors
>>>>have an alpha value of 0. How can I generate a graphic that is
>>>>completel y transparent in certain areas (so that the web page background
>>>>shows through)? I save my graphics as gif files. I would appreciate, if
>>>>possible, a simple example so that I can see the code. Thanks.
>>>> --
>>>> Nathan Sokalski
>>>> njsokalski@hotm ail.com
>>>> http://www.nathansokalski.com/
>>>>
>>>
>>>[/color]
>>
>>[/color]
>
>[/color]

[Lloyd Dupont]

Re: Transparency, ASP.NET, and GDI+

mmhh...
never really investigate this matter, but I would have guess that maybe you
could do:

Bitmap bmp = new Bitmap(width, height);
bmp.MakeTranspa rent();

or with
bmp.LockBit() you could directly access the bitmap's color pointer
as explained here:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dncscol/html/csharp11152001.asp

[Kevin Spencer]

Re: Transparency, ASP.NET, and GDI+

Not correct. While IE doesn't support PNG transparency, it has lawys
supported GIF transparency.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
Everybody picks their nose,
But some people are better at hiding it.

"Lloyd Dupont" <net.galador@ld > wrote in message
news:eyb0iUunFH A.3120@TK2MSFTN GP09.phx.gbl...[color=blue]
>I think IE don't support transparency.
> At least I can say for sure it doesn't support PNG transparency.
> It is an issue that should be fixed with IE 7 or could be fixd with
> Firefox!
>
> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
> news:On0xnMtnFH A.2916@TK2MSFTN GP14.phx.gbl...[color=green]
>> Like I said in my original message, I am using GIF. The line that I use
>> to save my image is as follows (testbitmap is the name of my
>> System.Drawing. Bitmap object):
>>
>> testbitmap.Save (Server.MapPath ("GDItest.gif") , Imaging.ImageFo rmat.Gif)
>>
>> --
>> Nathan Sokalski
>> njsokalski@hotm ail.com
>> http://www.nathansokalski.com/
>>
>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>> news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...[color=darkred]
>>> The only graphics formats that have transparency in HTML are GIF and
>>> PNG. What format are you using?
>>>
>>> --
>>> HTH,
>>>
>>> Kevin Spencer
>>> Microsoft MVP
>>> .Net Developer
>>> Everybody picks their nose,
>>> But some people are better at hiding it.
>>>
>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>I am trying to create graphics with GDI+ that include transparency.
>>>>However, the transparency never seems to show up, even though my colors
>>>>have an alpha value of 0. How can I generate a graphic that is
>>>>completel y transparent in certain areas (so that the web page background
>>>>shows through)? I save my graphics as gif files. I would appreciate, if
>>>>possible, a simple example so that I can see the code. Thanks.
>>>> --
>>>> Nathan Sokalski
>>>> njsokalski@hotm ail.com
>>>> http://www.nathansokalski.com/
>>>>
>>>
>>>[/color]
>>
>>[/color]
>
>[/color]

[Kevin Spencer]

Re: Transparency, ASP.NET, and GDI+

Hi Nathan,

Sorry, I missed the "gif" reference in your OP.

A GIF image palette can define one color as transparent. I'm not sure how
you're defining the transparent color in your palette, but the following
Microsoft KB article explains how to do it. Note that the article is not
specifically about making a transparent gif, but it covers creating a
palette with a single transparent color, which is encoded as the transparent
color for the GIF:

http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q319061

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
Everybody picks their nose,
But some people are better at hiding it.

"Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
news:On0xnMtnFH A.2916@TK2MSFTN GP14.phx.gbl...[color=blue]
> Like I said in my original message, I am using GIF. The line that I use to
> save my image is as follows (testbitmap is the name of my
> System.Drawing. Bitmap object):
>
> testbitmap.Save (Server.MapPath ("GDItest.gif") , Imaging.ImageFo rmat.Gif)
>
> --
> Nathan Sokalski
> njsokalski@hotm ail.com
> http://www.nathansokalski.com/
>
> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
> news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...[color=green]
>> The only graphics formats that have transparency in HTML are GIF and PNG.
>> What format are you using?
>>
>> --
>> HTH,
>>
>> Kevin Spencer
>> Microsoft MVP
>> .Net Developer
>> Everybody picks their nose,
>> But some people are better at hiding it.
>>
>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...[color=darkred]
>>>I am trying to create graphics with GDI+ that include transparency.
>>>However, the transparency never seems to show up, even though my colors
>>>have an alpha value of 0. How can I generate a graphic that is completely
>>>transparen t in certain areas (so that the web page background shows
>>>through)? I save my graphics as gif files. I would appreciate, if
>>>possible, a simple example so that I can see the code. Thanks.
>>> --
>>> Nathan Sokalski
>>> njsokalski@hotm ail.com
>>> http://www.nathansokalski.com/
>>>[/color]
>>
>>[/color]
>
>[/color]

[Nathan Sokalski]

Re: Transparency, ASP.NET, and GDI+

The MakeTransparent () didn't seem to have any affect, and I'm not sure why
(maybe the example wasn't quite clear enough) but the link you gave didn't
seem very clear to me. I think what I really need is a just a basic example
that just draws a simple shape or two and then adds a transparent area.
Thanks.
--
Nathan Sokalski
njsokalski@hotm ail.com

http://www.nathansokalski.com/

"Lloyd Dupont" <net.galador@ld > wrote in message
news:OMrxPhvnFH A.2904@tk2msftn gp13.phx.gbl...[color=blue]
> mmhh...
> never really investigate this matter, but I would have guess that maybe
> you could do:
>
> Bitmap bmp = new Bitmap(width, height);
> bmp.MakeTranspa rent();
>
> or with
> bmp.LockBit() you could directly access the bitmap's color pointer
> as explained here:
> http://msdn.microsoft.com/library/de...rp11152001.asp
>[/color]

[Nathan Sokalski]

Re: Transparency, ASP.NET, and GDI+

I looked at the article you mentioned, and it definitely cleared up for me
why I was never getting any transparency, but I am still having trouble
figuring out how to fix the problem. I think what I really need is just a
basic example that just draws a simple shape or two and then adds a
transparent area. (Preferably in VB.NET, but I can usually get enough from
C# that it helps enough to solve my problem) Thanks.
--
Nathan Sokalski
njsokalski@hotm ail.com

http://www.nathansokalski.com/

"Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
news:%2335It9yn FHA.3380@TK2MSF TNGP12.phx.gbl. ..[color=blue]
> Hi Nathan,
>
> Sorry, I missed the "gif" reference in your OP.
>
> A GIF image palette can define one color as transparent. I'm not sure how
> you're defining the transparent color in your palette, but the following
> Microsoft KB article explains how to do it. Note that the article is not
> specifically about making a transparent gif, but it covers creating a
> palette with a single transparent color, which is encoded as the
> transparent color for the GIF:
>
> http://support.microsoft.com/default...;EN-US;Q319061
>
> --
> HTH,
>
> Kevin Spencer
> Microsoft MVP
> .Net Developer
> Everybody picks their nose,
> But some people are better at hiding it.
>
> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
> news:On0xnMtnFH A.2916@TK2MSFTN GP14.phx.gbl...[color=green]
>> Like I said in my original message, I am using GIF. The line that I use
>> to save my image is as follows (testbitmap is the name of my
>> System.Drawing. Bitmap object):
>>
>> testbitmap.Save (Server.MapPath ("GDItest.gif") , Imaging.ImageFo rmat.Gif)
>>
>> --
>> Nathan Sokalski
>> njsokalski@hotm ail.com
>> http://www.nathansokalski.com/
>>
>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>> news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...[color=darkred]
>>> The only graphics formats that have transparency in HTML are GIF and
>>> PNG. What format are you using?
>>>
>>> --
>>> HTH,
>>>
>>> Kevin Spencer
>>> Microsoft MVP
>>> .Net Developer
>>> Everybody picks their nose,
>>> But some people are better at hiding it.
>>>
>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>I am trying to create graphics with GDI+ that include transparency.
>>>>However, the transparency never seems to show up, even though my colors
>>>>have an alpha value of 0. How can I generate a graphic that is
>>>>completel y transparent in certain areas (so that the web page background
>>>>shows through)? I save my graphics as gif files. I would appreciate, if
>>>>possible, a simple example so that I can see the code. Thanks.
>>>> --
>>>> Nathan Sokalski
>>>> njsokalski@hotm ail.com
>>>> http://www.nathansokalski.com/
>>>>
>>>
>>>[/color]
>>
>>[/color]
>
>[/color]

[Kevin Spencer]

Re: Transparency, ASP.NET, and GDI+

Hi Nathan,

Okay, basically you have a palette to work with. The article tells you how
to define the colors in the palette. Also note that the palette can
certainly have LESS than 256 colors if you don't need them all. So, assuming
you're drawing with GDI+, you just clear the bitmap to the transparent
color, and draw with the others. All of the pixels that have the transparent
color will be transparent. It doesn't matter what the transparent color is;
it will be defined as "the transparent color" in the palette.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
Expect the unaccepted.

"Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
news:%23daSLW3n FHA.1996@TK2MSF TNGP10.phx.gbl. ..[color=blue]
>I looked at the article you mentioned, and it definitely cleared up for me
>why I was never getting any transparency, but I am still having trouble
>figuring out how to fix the problem. I think what I really need is just a
>basic example that just draws a simple shape or two and then adds a
>transparent area. (Preferably in VB.NET, but I can usually get enough from
>C# that it helps enough to solve my problem) Thanks.
> --
> Nathan Sokalski
> njsokalski@hotm ail.com
> http://www.nathansokalski.com/
>
> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
> news:%2335It9yn FHA.3380@TK2MSF TNGP12.phx.gbl. ..[color=green]
>> Hi Nathan,
>>
>> Sorry, I missed the "gif" reference in your OP.
>>
>> A GIF image palette can define one color as transparent. I'm not sure how
>> you're defining the transparent color in your palette, but the following
>> Microsoft KB article explains how to do it. Note that the article is not
>> specifically about making a transparent gif, but it covers creating a
>> palette with a single transparent color, which is encoded as the
>> transparent color for the GIF:
>>
>> http://support.microsoft.com/default...;EN-US;Q319061
>>
>> --
>> HTH,
>>
>> Kevin Spencer
>> Microsoft MVP
>> .Net Developer
>> Everybody picks their nose,
>> But some people are better at hiding it.
>>
>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>> news:On0xnMtnFH A.2916@TK2MSFTN GP14.phx.gbl...[color=darkred]
>>> Like I said in my original message, I am using GIF. The line that I use
>>> to save my image is as follows (testbitmap is the name of my
>>> System.Drawing. Bitmap object):
>>>
>>> testbitmap.Save (Server.MapPath ("GDItest.gif") , Imaging.ImageFo rmat.Gif)
>>>
>>> --
>>> Nathan Sokalski
>>> njsokalski@hotm ail.com
>>> http://www.nathansokalski.com/
>>>
>>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>>> news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>> The only graphics formats that have transparency in HTML are GIF and
>>>> PNG. What format are you using?
>>>>
>>>> --
>>>> HTH,
>>>>
>>>> Kevin Spencer
>>>> Microsoft MVP
>>>> .Net Developer
>>>> Everybody picks their nose,
>>>> But some people are better at hiding it.
>>>>
>>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>>> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>>I am trying to create graphics with GDI+ that include transparency.
>>>>>However, the transparency never seems to show up, even though my colors
>>>>>have an alpha value of 0. How can I generate a graphic that is
>>>>>complete ly transparent in certain areas (so that the web page
>>>>>backgrou nd shows through)? I save my graphics as gif files. I would
>>>>>appreciate , if possible, a simple example so that I can see the code.
>>>>>Thanks.
>>>>> --
>>>>> Nathan Sokalski
>>>>> njsokalski@hotm ail.com
>>>>> http://www.nathansokalski.com/
>>>>>
>>>>
>>>>
>>>
>>>[/color]
>>
>>[/color]
>
>[/color]

[Lloyd Dupont]

Re: Transparency, ASP.NET, and GDI+

oops.. GIF!
what about
Bitmap.MakeTran sparent (Color)
where Color is your background which might be white per default, I believe

--
If you're in a war, instead of throwing a hand grenade at the enemy, throw
one of those small pumpkins. Maybe it'll make everyone think how stupid war
is, and while they are thinking, you can throw a real grenade at them.
Jack Handey.
"Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
news:OlQAv83nFH A.3448@TK2MSFTN GP12.phx.gbl...[color=blue]
> Hi Nathan,
>
> Okay, basically you have a palette to work with. The article tells you how
> to define the colors in the palette. Also note that the palette can
> certainly have LESS than 256 colors if you don't need them all. So,
> assuming you're drawing with GDI+, you just clear the bitmap to the
> transparent color, and draw with the others. All of the pixels that have
> the transparent color will be transparent. It doesn't matter what the
> transparent color is; it will be defined as "the transparent color" in the
> palette.
>
> --
> HTH,
>
> Kevin Spencer
> Microsoft MVP
> .Net Developer
> Expect the unaccepted.
>
> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
> news:%23daSLW3n FHA.1996@TK2MSF TNGP10.phx.gbl. ..[color=green]
>>I looked at the article you mentioned, and it definitely cleared up for me
>>why I was never getting any transparency, but I am still having trouble
>>figuring out how to fix the problem. I think what I really need is just a
>>basic example that just draws a simple shape or two and then adds a
>>transparent area. (Preferably in VB.NET, but I can usually get enough from
>>C# that it helps enough to solve my problem) Thanks.
>> --
>> Nathan Sokalski
>> njsokalski@hotm ail.com
>> http://www.nathansokalski.com/
>>
>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>> news:%2335It9yn FHA.3380@TK2MSF TNGP12.phx.gbl. ..[color=darkred]
>>> Hi Nathan,
>>>
>>> Sorry, I missed the "gif" reference in your OP.
>>>
>>> A GIF image palette can define one color as transparent. I'm not sure
>>> how you're defining the transparent color in your palette, but the
>>> following Microsoft KB article explains how to do it. Note that the
>>> article is not specifically about making a transparent gif, but it
>>> covers creating a palette with a single transparent color, which is
>>> encoded as the transparent color for the GIF:
>>>
>>> http://support.microsoft.com/default...;EN-US;Q319061
>>>
>>> --
>>> HTH,
>>>
>>> Kevin Spencer
>>> Microsoft MVP
>>> .Net Developer
>>> Everybody picks their nose,
>>> But some people are better at hiding it.
>>>
>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>> news:On0xnMtnFH A.2916@TK2MSFTN GP14.phx.gbl...
>>>> Like I said in my original message, I am using GIF. The line that I use
>>>> to save my image is as follows (testbitmap is the name of my
>>>> System.Drawing. Bitmap object):
>>>>
>>>> testbitmap.Save (Server.MapPath ("GDItest.gif") , Imaging.ImageFo rmat.Gif)
>>>>
>>>> --
>>>> Nathan Sokalski
>>>> njsokalski@hotm ail.com
>>>> http://www.nathansokalski.com/
>>>>
>>>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>>>> news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>> The only graphics formats that have transparency in HTML are GIF and
>>>>> PNG. What format are you using?
>>>>>
>>>>> --
>>>>> HTH,
>>>>>
>>>>> Kevin Spencer
>>>>> Microsoft MVP
>>>>> .Net Developer
>>>>> Everybody picks their nose,
>>>>> But some people are better at hiding it.
>>>>>
>>>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>>>> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>>>I am trying to create graphics with GDI+ that include transparency.
>>>>>>However , the transparency never seems to show up, even though my
>>>>>>colors have an alpha value of 0. How can I generate a graphic that is
>>>>>>completel y transparent in certain areas (so that the web page
>>>>>>backgroun d shows through)? I save my graphics as gif files. I would
>>>>>>appreciat e, if possible, a simple example so that I can see the code.
>>>>>>Thanks.
>>>>>> --
>>>>>> Nathan Sokalski
>>>>>> njsokalski@hotm ail.com
>>>>>> http://www.nathansokalski.com/
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>[/color]
>>
>>[/color]
>
>[/color]

[Nathan Sokalski]

Re: Transparency, ASP.NET, and GDI+

I am having trouble defining the colors in the palette. The first method I
tried gave me the error Object reference not set to an instance of an
object. (Which didn't surprise me, but it would not let me use the keyword
New when declaring the Imaging.ColorPa lette). Here is that code:

Dim transbitmap As New Bitmap(400, 400)
Dim transgraphics As Graphics = Graphics.FromIm age(transbitmap )
Dim transpen As New Pen(Color.FromA rgb(255, 0, 255, 0), 20)
Dim transbrush As New SolidBrush(Colo r.FromArgb(255, 255, 0, 0))
Dim transpalette As Imaging.ColorPa lette
transpalette.En tries(0) = Color.FromArgb( 0, 255, 255, 255)
transpalette.En tries(1) = Color.FromArgb( 255, 0, 255, 0)
transpalette.En tries(2) = Color.FromArgb( 255, 255, 0, 0)

transgraphics.C lear(Color.From Argb(0, 255, 255, 255))
transbitmap.Pal ette = transpalette
transgraphics.F illRectangle(tr ansbrush, 100, 100, 200, 200)
transgraphics.D rawRectangle(tr anspen, 50, 50, 150, 150)
transbitmap.Sav e(Server.MapPat h("GDItest.gif" ), Imaging.ImageFo rmat.Gif)


The second method I tried gave me the error Index was outside the bounds of
the array. Here is that code:

Dim transbitmap As New Bitmap(400, 400)
Dim transgraphics As Graphics = Graphics.FromIm age(transbitmap )
Dim transpen As New Pen(Color.FromA rgb(255, 0, 255, 0), 20)
Dim transbrush As New SolidBrush(Colo r.FromArgb(255, 255, 0, 0))
transbitmap.Pal ette.Entries(0) = Color.FromArgb( 0, 255, 255, 255)
transbitmap.Pal ette.Entries(1) = Color.FromArgb( 255, 0, 255, 0)
transbitmap.Pal ette.Entries(2) = Color.FromArgb( 255, 255, 0, 0)

transgraphics.C lear(Color.From Argb(0, 255, 255, 255))
transgraphics.F illRectangle(tr ansbrush, 100, 100, 200, 200)
transgraphics.D rawRectangle(tr anspen, 50, 50, 150, 150)
transbitmap.Sav e(Server.MapPat h("GDItest.gif" ), Imaging.ImageFo rmat.Gif)


What I expected from the code above was to create a GIF file with a red
filled rectangle, a green unfilled rectangle, and a transparent background.
If I remove the lines where I attempt to define the palette, this is what I
got except instead of a transparent background I ended up with a black
background. What am I supposed to do to create/edit the palette? The article
you mentioned took the palette from another Bitmap, which is not something I
am planning to do. Thanks.
--
Nathan Sokalski
njsokalski@hotm ail.com

http://www.nathansokalski.com/

"Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
news:OlQAv83nFH A.3448@TK2MSFTN GP12.phx.gbl...[color=blue]
> Hi Nathan,
>
> Okay, basically you have a palette to work with. The article tells you how
> to define the colors in the palette. Also note that the palette can
> certainly have LESS than 256 colors if you don't need them all. So,
> assuming you're drawing with GDI+, you just clear the bitmap to the
> transparent color, and draw with the others. All of the pixels that have
> the transparent color will be transparent. It doesn't matter what the
> transparent color is; it will be defined as "the transparent color" in the
> palette.
>
> --
> HTH,
>
> Kevin Spencer
> Microsoft MVP
> .Net Developer
> Expect the unaccepted.
>
> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
> news:%23daSLW3n FHA.1996@TK2MSF TNGP10.phx.gbl. ..[color=green]
>>I looked at the article you mentioned, and it definitely cleared up for me
>>why I was never getting any transparency, but I am still having trouble
>>figuring out how to fix the problem. I think what I really need is just a
>>basic example that just draws a simple shape or two and then adds a
>>transparent area. (Preferably in VB.NET, but I can usually get enough from
>>C# that it helps enough to solve my problem) Thanks.
>> --
>> Nathan Sokalski
>> njsokalski@hotm ail.com
>> http://www.nathansokalski.com/
>>
>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>> news:%2335It9yn FHA.3380@TK2MSF TNGP12.phx.gbl. ..[color=darkred]
>>> Hi Nathan,
>>>
>>> Sorry, I missed the "gif" reference in your OP.
>>>
>>> A GIF image palette can define one color as transparent. I'm not sure
>>> how you're defining the transparent color in your palette, but the
>>> following Microsoft KB article explains how to do it. Note that the
>>> article is not specifically about making a transparent gif, but it
>>> covers creating a palette with a single transparent color, which is
>>> encoded as the transparent color for the GIF:
>>>
>>> http://support.microsoft.com/default...;EN-US;Q319061
>>>
>>> --
>>> HTH,
>>>
>>> Kevin Spencer
>>> Microsoft MVP
>>> .Net Developer
>>> Everybody picks their nose,
>>> But some people are better at hiding it.
>>>
>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>> news:On0xnMtnFH A.2916@TK2MSFTN GP14.phx.gbl...
>>>> Like I said in my original message, I am using GIF. The line that I use
>>>> to save my image is as follows (testbitmap is the name of my
>>>> System.Drawing. Bitmap object):
>>>>
>>>> testbitmap.Save (Server.MapPath ("GDItest.gif") , Imaging.ImageFo rmat.Gif)
>>>>
>>>> --
>>>> Nathan Sokalski
>>>> njsokalski@hotm ail.com
>>>> http://www.nathansokalski.com/
>>>>
>>>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>>>> news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>> The only graphics formats that have transparency in HTML are GIF and
>>>>> PNG. What format are you using?
>>>>>
>>>>> --
>>>>> HTH,
>>>>>
>>>>> Kevin Spencer
>>>>> Microsoft MVP
>>>>> .Net Developer
>>>>> Everybody picks their nose,
>>>>> But some people are better at hiding it.
>>>>>
>>>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>>>> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>>>I am trying to create graphics with GDI+ that include transparency.
>>>>>>However , the transparency never seems to show up, even though my
>>>>>>colors have an alpha value of 0. How can I generate a graphic that is
>>>>>>completel y transparent in certain areas (so that the web page
>>>>>>backgroun d shows through)? I save my graphics as gif files. I would
>>>>>>appreciat e, if possible, a simple example so that I can see the code.
>>>>>>Thanks.
>>>>>> --
>>>>>> Nathan Sokalski
>>>>>> njsokalski@hotm ail.com
>>>>>> http://www.nathansokalski.com/
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>[/color]
>>
>>[/color]
>
>[/color]

[Nathan Sokalski]

Re: Transparency, ASP.NET, and GDI+

I tried putting a color inside the MakeTransparent method, but it not only
did not make it transparent, but prevented all of the other stuff from being
drawn as well. Here is my code (note that the Clear method has the same
color as the MakeTransparent method):

Dim transbitmap As New Bitmap(400, 400)
Dim transgraphics As Graphics = Graphics.FromIm age(transbitmap )
Dim transpen As New Pen(Color.FromA rgb(255, 0, 255, 0), 20)
Dim transbrush As New SolidBrush(Colo r.FromArgb(255, 255, 0, 0))

transgraphics.C lear(Color.From Argb(0, 255, 255, 255))
transbitmap.Mak eTransparent(Co lor.FromArgb(0, 255, 255, 255))
transgraphics.F illRectangle(tr ansbrush, 100, 100, 200, 200)
transgraphics.D rawRectangle(tr anspen, 50, 50, 150, 150)
transbitmap.Sav e(Server.MapPat h("GDItest.gif" ), Imaging.ImageFo rmat.Gif)

Is there something wrong with the way I am using the MakeTransparent method?
What do I need to do to make areas of my image transparent? Thanks.
--
Nathan Sokalski
njsokalski@hotm ail.com

http://www.nathansokalski.com/

"Lloyd Dupont" <ld@NewsAccount .galador.net> wrote in message
news:OxeBOj5nFH A.3408@tk2msftn gp13.phx.gbl...[color=blue]
> oops.. GIF!
> what about
> Bitmap.MakeTran sparent (Color)
> where Color is your background which might be white per default, I believe
>
> --
> If you're in a war, instead of throwing a hand grenade at the enemy, throw
> one of those small pumpkins. Maybe it'll make everyone think how stupid
> war is, and while they are thinking, you can throw a real grenade at them.
> Jack Handey.
> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
> news:OlQAv83nFH A.3448@TK2MSFTN GP12.phx.gbl...[color=green]
>> Hi Nathan,
>>
>> Okay, basically you have a palette to work with. The article tells you
>> how to define the colors in the palette. Also note that the palette can
>> certainly have LESS than 256 colors if you don't need them all. So,
>> assuming you're drawing with GDI+, you just clear the bitmap to the
>> transparent color, and draw with the others. All of the pixels that have
>> the transparent color will be transparent. It doesn't matter what the
>> transparent color is; it will be defined as "the transparent color" in
>> the palette.
>>
>> --
>> HTH,
>>
>> Kevin Spencer
>> Microsoft MVP
>> .Net Developer
>> Expect the unaccepted.
>>
>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>> news:%23daSLW3n FHA.1996@TK2MSF TNGP10.phx.gbl. ..[color=darkred]
>>>I looked at the article you mentioned, and it definitely cleared up for
>>>me why I was never getting any transparency, but I am still having
>>>trouble figuring out how to fix the problem. I think what I really need
>>>is just a basic example that just draws a simple shape or two and then
>>>adds a transparent area. (Preferably in VB.NET, but I can usually get
>>>enough from C# that it helps enough to solve my problem) Thanks.
>>> --
>>> Nathan Sokalski
>>> njsokalski@hotm ail.com
>>> http://www.nathansokalski.com/
>>>
>>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>>> news:%2335It9yn FHA.3380@TK2MSF TNGP12.phx.gbl. ..
>>>> Hi Nathan,
>>>>
>>>> Sorry, I missed the "gif" reference in your OP.
>>>>
>>>> A GIF image palette can define one color as transparent. I'm not sure
>>>> how you're defining the transparent color in your palette, but the
>>>> following Microsoft KB article explains how to do it. Note that the
>>>> article is not specifically about making a transparent gif, but it
>>>> covers creating a palette with a single transparent color, which is
>>>> encoded as the transparent color for the GIF:
>>>>
>>>> http://support.microsoft.com/default...;EN-US;Q319061
>>>>
>>>> --
>>>> HTH,
>>>>
>>>> Kevin Spencer
>>>> Microsoft MVP
>>>> .Net Developer
>>>> Everybody picks their nose,
>>>> But some people are better at hiding it.
>>>>
>>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>>> news:On0xnMtnFH A.2916@TK2MSFTN GP14.phx.gbl...
>>>>> Like I said in my original message, I am using GIF. The line that I
>>>>> use to save my image is as follows (testbitmap is the name of my
>>>>> System.Drawing. Bitmap object):
>>>>>
>>>>> testbitmap.Save (Server.MapPath ("GDItest.gif") ,
>>>>> Imaging.ImageFo rmat.Gif)
>>>>>
>>>>> --
>>>>> Nathan Sokalski
>>>>> njsokalski@hotm ail.com
>>>>> http://www.nathansokalski.com/
>>>>>
>>>>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>>>>> news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>>> The only graphics formats that have transparency in HTML are GIF and
>>>>>> PNG. What format are you using?
>>>>>>
>>>>>> --
>>>>>> HTH,
>>>>>>
>>>>>> Kevin Spencer
>>>>>> Microsoft MVP
>>>>>> .Net Developer
>>>>>> Everybody picks their nose,
>>>>>> But some people are better at hiding it.
>>>>>>
>>>>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>>>>> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>>>>I am trying to create graphics with GDI+ that include transparency.
>>>>>>>Howeve r, the transparency never seems to show up, even though my
>>>>>>>colors have an alpha value of 0. How can I generate a graphic that is
>>>>>>>complete ly transparent in certain areas (so that the web page
>>>>>>>backgrou nd shows through)? I save my graphics as gif files. I would
>>>>>>>apprecia te, if possible, a simple example so that I can see the code.
>>>>>>>Thanks .
>>>>>>> --
>>>>>>> Nathan Sokalski
>>>>>>> njsokalski@hotm ail.com
>>>>>>> http://www.nathansokalski.com/
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>[/color]
>>
>>[/color]
>
>[/color]

[Lloyd Dupont]

Re: Transparency, ASP.NET, and GDI+

GWBYF (aka Google Would Be Your Friend != RTFM)

http://www.bobpowell.net/giftransparency.htm

--
If you're in a war, instead of throwing a hand grenade at the enemy, throw
one of those small pumpkins. Maybe it'll make everyone think how stupid war
is, and while they are thinking, you can throw a real grenade at them.
Jack Handey.
"Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
news:%23SuMEt6n FHA.3544@TK2MSF TNGP15.phx.gbl. ..[color=blue]
>I tried putting a color inside the MakeTransparent method, but it not only
>did not make it transparent, but prevented all of the other stuff from
>being drawn as well. Here is my code (note that the Clear method has the
>same color as the MakeTransparent method):
>
> Dim transbitmap As New Bitmap(400, 400)
> Dim transgraphics As Graphics = Graphics.FromIm age(transbitmap )
> Dim transpen As New Pen(Color.FromA rgb(255, 0, 255, 0), 20)
> Dim transbrush As New SolidBrush(Colo r.FromArgb(255, 255, 0, 0))
>
> transgraphics.C lear(Color.From Argb(0, 255, 255, 255))
> transbitmap.Mak eTransparent(Co lor.FromArgb(0, 255, 255, 255))
> transgraphics.F illRectangle(tr ansbrush, 100, 100, 200, 200)
> transgraphics.D rawRectangle(tr anspen, 50, 50, 150, 150)
> transbitmap.Sav e(Server.MapPat h("GDItest.gif" ), Imaging.ImageFo rmat.Gif)
>
> Is there something wrong with the way I am using the MakeTransparent
> method? What do I need to do to make areas of my image transparent?
> Thanks.
> --
> Nathan Sokalski
> njsokalski@hotm ail.com
> http://www.nathansokalski.com/
>
> "Lloyd Dupont" <ld@NewsAccount .galador.net> wrote in message
> news:OxeBOj5nFH A.3408@tk2msftn gp13.phx.gbl...[color=green]
>> oops.. GIF!
>> what about
>> Bitmap.MakeTran sparent (Color)
>> where Color is your background which might be white per default, I
>> believe
>>
>> --
>> If you're in a war, instead of throwing a hand grenade at the enemy,
>> throw one of those small pumpkins. Maybe it'll make everyone think how
>> stupid war is, and while they are thinking, you can throw a real grenade
>> at them.
>> Jack Handey.
>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>> news:OlQAv83nFH A.3448@TK2MSFTN GP12.phx.gbl...[color=darkred]
>>> Hi Nathan,
>>>
>>> Okay, basically you have a palette to work with. The article tells you
>>> how to define the colors in the palette. Also note that the palette can
>>> certainly have LESS than 256 colors if you don't need them all. So,
>>> assuming you're drawing with GDI+, you just clear the bitmap to the
>>> transparent color, and draw with the others. All of the pixels that have
>>> the transparent color will be transparent. It doesn't matter what the
>>> transparent color is; it will be defined as "the transparent color" in
>>> the palette.
>>>
>>> --
>>> HTH,
>>>
>>> Kevin Spencer
>>> Microsoft MVP
>>> .Net Developer
>>> Expect the unaccepted.
>>>
>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>> news:%23daSLW3n FHA.1996@TK2MSF TNGP10.phx.gbl. ..
>>>>I looked at the article you mentioned, and it definitely cleared up for
>>>>me why I was never getting any transparency, but I am still having
>>>>trouble figuring out how to fix the problem. I think what I really need
>>>>is just a basic example that just draws a simple shape or two and then
>>>>adds a transparent area. (Preferably in VB.NET, but I can usually get
>>>>enough from C# that it helps enough to solve my problem) Thanks.
>>>> --
>>>> Nathan Sokalski
>>>> njsokalski@hotm ail.com
>>>> http://www.nathansokalski.com/
>>>>
>>>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>>>> news:%2335It9yn FHA.3380@TK2MSF TNGP12.phx.gbl. ..
>>>>> Hi Nathan,
>>>>>
>>>>> Sorry, I missed the "gif" reference in your OP.
>>>>>
>>>>> A GIF image palette can define one color as transparent. I'm not sure
>>>>> how you're defining the transparent color in your palette, but the
>>>>> following Microsoft KB article explains how to do it. Note that the
>>>>> article is not specifically about making a transparent gif, but it
>>>>> covers creating a palette with a single transparent color, which is
>>>>> encoded as the transparent color for the GIF:
>>>>>
>>>>> http://support.microsoft.com/default...;EN-US;Q319061
>>>>>
>>>>> --
>>>>> HTH,
>>>>>
>>>>> Kevin Spencer
>>>>> Microsoft MVP
>>>>> .Net Developer
>>>>> Everybody picks their nose,
>>>>> But some people are better at hiding it.
>>>>>
>>>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>>>> news:On0xnMtnFH A.2916@TK2MSFTN GP14.phx.gbl...
>>>>>> Like I said in my original message, I am using GIF. The line that I
>>>>>> use to save my image is as follows (testbitmap is the name of my
>>>>>> System.Drawing. Bitmap object):
>>>>>>
>>>>>> testbitmap.Save (Server.MapPath ("GDItest.gif") ,
>>>>>> Imaging.ImageFo rmat.Gif)
>>>>>>
>>>>>> --
>>>>>> Nathan Sokalski
>>>>>> njsokalski@hotm ail.com
>>>>>> http://www.nathansokalski.com/
>>>>>>
>>>>>> "Kevin Spencer" <kevin@DIESPAMM ERSDIEtakempis. com> wrote in message
>>>>>> news:eq$BVdrnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>>>> The only graphics formats that have transparency in HTML are GIF and
>>>>>>> PNG. What format are you using?
>>>>>>>
>>>>>>> --
>>>>>>> HTH,
>>>>>>>
>>>>>>> Kevin Spencer
>>>>>>> Microsoft MVP
>>>>>>> .Net Developer
>>>>>>> Everybody picks their nose,
>>>>>>> But some people are better at hiding it.
>>>>>>>
>>>>>>> "Nathan Sokalski" <njsokalski@hot mail.com> wrote in message
>>>>>>> news:OtgRhOqnFH A.3936@TK2MSFTN GP10.phx.gbl...
>>>>>>>>I am trying to create graphics with GDI+ that include transparency.
>>>>>>>>However , the transparency never seems to show up, even though my
>>>>>>>>color s have an alpha value of 0. How can I generate a graphic that
>>>>>>>>is completely transparent in certain areas (so that the web page
>>>>>>>>backgro und shows through)? I save my graphics as gif files. I would
>>>>>>>>appreci ate, if possible, a simple example so that I can see the
>>>>>>>>code. Thanks.
>>>>>>>> --
>>>>>>>> Nathan Sokalski
>>>>>>>> njsokalski@hotm ail.com
>>>>>>>> http://www.nathansokalski.com/
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>[/color]
>>
>>[/color]
>
>[/color]