A paint event question

Re: A paint event question

Hi,

"hamil" <hamil@discussi ons.microsoft.c om> wrote in message
news:EDE7C508-8803-46E5-ADEE-6E85326448A6@mi crosoft.com...[color=blue]
> The following code will display a tif file on a form. When another form is
> moved over the tif image, the tif image is erased where the form was
> moved.
> A paint event occurs when this happens. My question is..how would I save
> the
> tif images as soon as it is initially painted, and then restore the image
> in
> a paint event. It seems to me that there should be some sort of a
> SaveImage[/color]

But why would you want to save and restore it, it is already in a Bitmap,
just (re)draw it inside OnPaint. Also, never store a Graphics object
obtained with CreateGraphics, you must always Dispose it before the
eventhandler finishes.

See code below.
[color=blue]
> method and a RestoreImage method that would be fast. Note: Page1 is the
> form
> name, and FileName is passed from a routine on another form.[/color]

Public Filename as String
Dim bm As Bitmap

Public Sub DrawTif()
bm = Bitmap.FromFile (FileName)
End Sub

Sub Page1_paint
If ( Not bm Is Nothing ) Then
e.Graphics.Inte rpolationMode =
Drawing2D.Inter polationMode.Hi ghQualityBicubi c
e.DrawImage(bm, New Rectangle(0, 0, 400, 500))
End If
End sub

Sub Page1_Closing
bm.Dispose
bm = Nothing
End Sub

HTH,
Greetings

Re: A paint event question



"Bart Mermuys" wrote:
[color=blue]
> Hi,
>
> "hamil" <hamil@discussi ons.microsoft.c om> wrote in message
> news:EDE7C508-8803-46E5-ADEE-6E85326448A6@mi crosoft.com...[color=green]
> > The following code will display a tif file on a form. When another form is
> > moved over the tif image, the tif image is erased where the form was
> > moved.
> > A paint event occurs when this happens. My question is..how would I save
> > the
> > tif images as soon as it is initially painted, and then restore the image
> > in
> > a paint event. It seems to me that there should be some sort of a
> > SaveImage[/color]
>
> But why would you want to save and restore it, it is already in a Bitmap,
> just (re)draw it inside OnPaint. Also, never store a Graphics object
> obtained with CreateGraphics, you must always Dispose it before the
> eventhandler finishes.
>
> See code below.
>[color=green]
> > method and a RestoreImage method that would be fast. Note: Page1 is the
> > form
> > name, and FileName is passed from a routine on another form.[/color]
>
> Public Filename as String
> Dim bm As Bitmap
>
> Public Sub DrawTif()
> bm = Bitmap.FromFile (FileName)
> End Sub
>
> Sub Page1_paint
> If ( Not bm Is Nothing ) Then
> e.Graphics.Inte rpolationMode =
> Drawing2D.Inter polationMode.Hi ghQualityBicubi c
> e.DrawImage(bm, New Rectangle(0, 0, 400, 500))
> End If
> End sub
>
> Sub Page1_Closing
> bm.Dispose
> bm = Nothing
> End Sub
>
> HTH,
> Greetings
>
>
>[/color]
Bert..

Your code works, but the paint event is slow. My image is a tif that was
originally an 8-1/2 X 11 page, black-white sheet scanned at 300 DPI, that
results in about 8,200,000 pixels. I use a Group four Fax compression that
makes the file about 50K bytes. The code " bm = bitmap.from file..." will
decompress and regenerate the 8,200,000 bit image. Since I am now displaying
the image on a form on by screen at about 1100 X 850 pixels, (935,000 bits),
interpolation must be used along with the scaling to get a good image. I am
pretty sure the scaling and interpolation is what is taking up most of the
time as this is done at every paint event.

It seems to me that there should be some way to scale, interpolate, and draw
the image to a buffer that is saved. Then at the paint event, the buffer
could be read and drawn without having to go through the scaling and
interpolation every time.

Any thoughts here? Maybe this cannot be done in VB.

Hamil.

Re: A paint event question

Hi,

"hamil" <hamil@discussi ons.microsoft.c om> wrote in message
news:D44F685A-EFE6-4E4F-B004-E8690DF47835@mi crosoft.com...[color=blue]
>
>
> "Bart Mermuys" wrote:
>[color=green]
>> Hi,
>>
>> "hamil" <hamil@discussi ons.microsoft.c om> wrote in message
>> news:EDE7C508-8803-46E5-ADEE-6E85326448A6@mi crosoft.com...[color=darkred]
>> > The following code will display a tif file on a form. When another form
>> > is
>> > moved over the tif image, the tif image is erased where the form was
>> > moved.
>> > A paint event occurs when this happens. My question is..how would I
>> > save
>> > the
>> > tif images as soon as it is initially painted, and then restore the
>> > image
>> > in
>> > a paint event. It seems to me that there should be some sort of a
>> > SaveImage[/color]
>>
>> But why would you want to save and restore it, it is already in a Bitmap,
>> just (re)draw it inside OnPaint. Also, never store a Graphics object
>> obtained with CreateGraphics, you must always Dispose it before the
>> eventhandler finishes.
>>
>> See code below.
>>[color=darkred]
>> > method and a RestoreImage method that would be fast. Note: Page1 is the
>> > form
>> > name, and FileName is passed from a routine on another form.[/color]
>>
>> Public Filename as String
>> Dim bm As Bitmap
>>
>> Public Sub DrawTif()
>> bm = Bitmap.FromFile (FileName)
>> End Sub
>>
>> Sub Page1_paint
>> If ( Not bm Is Nothing ) Then
>> e.Graphics.Inte rpolationMode =
>> Drawing2D.Inter polationMode.Hi ghQualityBicubi c
>> e.DrawImage(bm, New Rectangle(0, 0, 400, 500))
>> End If
>> End sub
>>
>> Sub Page1_Closing
>> bm.Dispose
>> bm = Nothing
>> End Sub
>>
>> HTH,
>> Greetings
>>
>>
>>[/color]
> Bert..
>
> Your code works, but the paint event is slow. My image is a tif that was
> originally an 8-1/2 X 11 page, black-white sheet scanned at 300 DPI, that
> results in about 8,200,000 pixels. I use a Group four Fax compression that
> makes the file about 50K bytes. The code " bm = bitmap.from file..." will
> decompress and regenerate the 8,200,000 bit image. Since I am now
> displaying
> the image on a form on by screen at about 1100 X 850 pixels, (935,000
> bits),
> interpolation must be used along with the scaling to get a good image. I
> am
> pretty sure the scaling and interpolation is what is taking up most of the
> time as this is done at every paint event.
>
> It seems to me that there should be some way to scale, interpolate, and
> draw
> the image to a buffer that is saved. Then at the paint event, the buffer
> could be read and drawn without having to go through the scaling and
> interpolation every time.[/color]

You can draw the Bitmap from file into a memory Bitmap and then paint the
memory Bitmap inside onpaint, eg.:

Public Filename as String
Dim bm As Bitmap ' memory bitmap

Public Sub DrawTif()
Dim fileBitmap As Bitmap = Bitmap.FromFile (FileName)

' create memory bitmap
Dim gfx As Graphics = CreateGraphics( )
bm = New Bitmap( 400, 500, gfx )
gfx.Dispose()

' draw file-bitmap scaled into memory-bitmap
gfx = Graphics.FromIm age( bm )
gfx.Interpolati onMode = Drawing2D.Inter polationMode.Hi ghQualityBicubi c
gfx.DrawImage(f ileBitmap, New Rectangle(0, 0, 400, 500))
gfx.Dispose()

' dispose file bitmap
fileBitmap.Disp ose();

' trigger onpaint
Invalidate()
End Sub

Sub Page1_paint
If ( Not bm Is Nothing ) Then
e.Graphics.Draw ImageUnscaled(b m, 0, 0, 0, 0, 0 )
End If
End Sub

Sub Page1_Closing
bm.Dispose
bm = Nothing
End Sub

HTH,
Greetings

[color=blue]
>
> Any thoughts here? Maybe this cannot be done in VB.
>
> Hamil.
>[/color]

Re: A paint event question

If it's a large bitmap, wouldn't using BitBlt to copy the bitmap to the
graphics object passed in the paint event be much faster instead of drawimage?
--
Dennis in Houston


"Bart Mermuys" wrote:
[color=blue]
> Hi,
>
> "hamil" <hamil@discussi ons.microsoft.c om> wrote in message
> news:D44F685A-EFE6-4E4F-B004-E8690DF47835@mi crosoft.com...[color=green]
> >
> >
> > "Bart Mermuys" wrote:
> >[color=darkred]
> >> Hi,
> >>
> >> "hamil" <hamil@discussi ons.microsoft.c om> wrote in message
> >> news:EDE7C508-8803-46E5-ADEE-6E85326448A6@mi crosoft.com...
> >> > The following code will display a tif file on a form. When another form
> >> > is
> >> > moved over the tif image, the tif image is erased where the form was
> >> > moved.
> >> > A paint event occurs when this happens. My question is..how would I
> >> > save
> >> > the
> >> > tif images as soon as it is initially painted, and then restore the
> >> > image
> >> > in
> >> > a paint event. It seems to me that there should be some sort of a
> >> > SaveImage
> >>
> >> But why would you want to save and restore it, it is already in a Bitmap,
> >> just (re)draw it inside OnPaint. Also, never store a Graphics object
> >> obtained with CreateGraphics, you must always Dispose it before the
> >> eventhandler finishes.
> >>
> >> See code below.
> >>
> >> > method and a RestoreImage method that would be fast. Note: Page1 is the
> >> > form
> >> > name, and FileName is passed from a routine on another form.
> >>
> >> Public Filename as String
> >> Dim bm As Bitmap
> >>
> >> Public Sub DrawTif()
> >> bm = Bitmap.FromFile (FileName)
> >> End Sub
> >>
> >> Sub Page1_paint
> >> If ( Not bm Is Nothing ) Then
> >> e.Graphics.Inte rpolationMode =
> >> Drawing2D.Inter polationMode.Hi ghQualityBicubi c
> >> e.DrawImage(bm, New Rectangle(0, 0, 400, 500))
> >> End If
> >> End sub
> >>
> >> Sub Page1_Closing
> >> bm.Dispose
> >> bm = Nothing
> >> End Sub
> >>
> >> HTH,
> >> Greetings
> >>
> >>
> >>[/color]
> > Bert..
> >
> > Your code works, but the paint event is slow. My image is a tif that was
> > originally an 8-1/2 X 11 page, black-white sheet scanned at 300 DPI, that
> > results in about 8,200,000 pixels. I use a Group four Fax compression that
> > makes the file about 50K bytes. The code " bm = bitmap.from file..." will
> > decompress and regenerate the 8,200,000 bit image. Since I am now
> > displaying
> > the image on a form on by screen at about 1100 X 850 pixels, (935,000
> > bits),
> > interpolation must be used along with the scaling to get a good image. I
> > am
> > pretty sure the scaling and interpolation is what is taking up most of the
> > time as this is done at every paint event.
> >
> > It seems to me that there should be some way to scale, interpolate, and
> > draw
> > the image to a buffer that is saved. Then at the paint event, the buffer
> > could be read and drawn without having to go through the scaling and
> > interpolation every time.[/color]
>
> You can draw the Bitmap from file into a memory Bitmap and then paint the
> memory Bitmap inside onpaint, eg.:
>
> Public Filename as String
> Dim bm As Bitmap ' memory bitmap
>
> Public Sub DrawTif()
> Dim fileBitmap As Bitmap = Bitmap.FromFile (FileName)
>
> ' create memory bitmap
> Dim gfx As Graphics = CreateGraphics( )
> bm = New Bitmap( 400, 500, gfx )
> gfx.Dispose()
>
> ' draw file-bitmap scaled into memory-bitmap
> gfx = Graphics.FromIm age( bm )
> gfx.Interpolati onMode = Drawing2D.Inter polationMode.Hi ghQualityBicubi c
> gfx.DrawImage(f ileBitmap, New Rectangle(0, 0, 400, 500))
> gfx.Dispose()
>
> ' dispose file bitmap
> fileBitmap.Disp ose();
>
> ' trigger onpaint
> Invalidate()
> End Sub
>
> Sub Page1_paint
> If ( Not bm Is Nothing ) Then
> e.Graphics.Draw ImageUnscaled(b m, 0, 0, 0, 0, 0 )
> End If
> End Sub
>
> Sub Page1_Closing
> bm.Dispose
> bm = Nothing
> End Sub
>
> HTH,
> Greetings
>
>[color=green]
> >
> > Any thoughts here? Maybe this cannot be done in VB.
> >
> > Hamil.
> >[/color]
>
>
>[/color]

Re: A paint event question

Hi,

"Dennis" <Dennis@discuss ions.microsoft. com> wrote in message
news:3A9F8F5F-723D-46F8-9557-33639A2B93C5@mi crosoft.com...[color=blue]
> If it's a large bitmap, wouldn't using BitBlt to copy the bitmap to the
> graphics object passed in the paint event be much faster instead of
> drawimage?[/color]

BitBlt is GDI and DrawImage is GDI+, BitBlt will not scale but i guess you
could use it to transfer the memory Bitmap to the screen and maybe it will
be faster (i've heard GDI is faster then GDI+). Haven't tried it though.


HTH,
Greetings
[color=blue]
> --
> Dennis in Houston
>
>
> "Bart Mermuys" wrote:
>[color=green]
>> Hi,
>>
>> "hamil" <hamil@discussi ons.microsoft.c om> wrote in message
>> news:D44F685A-EFE6-4E4F-B004-E8690DF47835@mi crosoft.com...[color=darkred]
>> >
>> >
>> > "Bart Mermuys" wrote:
>> >
>> >> Hi,
>> >>
>> >> "hamil" <hamil@discussi ons.microsoft.c om> wrote in message
>> >> news:EDE7C508-8803-46E5-ADEE-6E85326448A6@mi crosoft.com...
>> >> > The following code will display a tif file on a form. When another
>> >> > form
>> >> > is
>> >> > moved over the tif image, the tif image is erased where the form was
>> >> > moved.
>> >> > A paint event occurs when this happens. My question is..how would I
>> >> > save
>> >> > the
>> >> > tif images as soon as it is initially painted, and then restore the
>> >> > image
>> >> > in
>> >> > a paint event. It seems to me that there should be some sort of a
>> >> > SaveImage
>> >>
>> >> But why would you want to save and restore it, it is already in a
>> >> Bitmap,
>> >> just (re)draw it inside OnPaint. Also, never store a Graphics object
>> >> obtained with CreateGraphics, you must always Dispose it before the
>> >> eventhandler finishes.
>> >>
>> >> See code below.
>> >>
>> >> > method and a RestoreImage method that would be fast. Note: Page1 is
>> >> > the
>> >> > form
>> >> > name, and FileName is passed from a routine on another form.
>> >>
>> >> Public Filename as String
>> >> Dim bm As Bitmap
>> >>
>> >> Public Sub DrawTif()
>> >> bm = Bitmap.FromFile (FileName)
>> >> End Sub
>> >>
>> >> Sub Page1_paint
>> >> If ( Not bm Is Nothing ) Then
>> >> e.Graphics.Inte rpolationMode =
>> >> Drawing2D.Inter polationMode.Hi ghQualityBicubi c
>> >> e.DrawImage(bm, New Rectangle(0, 0, 400, 500))
>> >> End If
>> >> End sub
>> >>
>> >> Sub Page1_Closing
>> >> bm.Dispose
>> >> bm = Nothing
>> >> End Sub
>> >>
>> >> HTH,
>> >> Greetings
>> >>
>> >>
>> >>
>> > Bert..
>> >
>> > Your code works, but the paint event is slow. My image is a tif that
>> > was
>> > originally an 8-1/2 X 11 page, black-white sheet scanned at 300 DPI,
>> > that
>> > results in about 8,200,000 pixels. I use a Group four Fax compression
>> > that
>> > makes the file about 50K bytes. The code " bm = bitmap.from file..."
>> > will
>> > decompress and regenerate the 8,200,000 bit image. Since I am now
>> > displaying
>> > the image on a form on by screen at about 1100 X 850 pixels, (935,000
>> > bits),
>> > interpolation must be used along with the scaling to get a good image.
>> > I
>> > am
>> > pretty sure the scaling and interpolation is what is taking up most of
>> > the
>> > time as this is done at every paint event.
>> >
>> > It seems to me that there should be some way to scale, interpolate, and
>> > draw
>> > the image to a buffer that is saved. Then at the paint event, the
>> > buffer
>> > could be read and drawn without having to go through the scaling and
>> > interpolation every time.[/color]
>>
>> You can draw the Bitmap from file into a memory Bitmap and then paint the
>> memory Bitmap inside onpaint, eg.:
>>
>> Public Filename as String
>> Dim bm As Bitmap ' memory bitmap
>>
>> Public Sub DrawTif()
>> Dim fileBitmap As Bitmap = Bitmap.FromFile (FileName)
>>
>> ' create memory bitmap
>> Dim gfx As Graphics = CreateGraphics( )
>> bm = New Bitmap( 400, 500, gfx )
>> gfx.Dispose()
>>
>> ' draw file-bitmap scaled into memory-bitmap
>> gfx = Graphics.FromIm age( bm )
>> gfx.Interpolati onMode = Drawing2D.Inter polationMode.Hi ghQualityBicubi c
>> gfx.DrawImage(f ileBitmap, New Rectangle(0, 0, 400, 500))
>> gfx.Dispose()
>>
>> ' dispose file bitmap
>> fileBitmap.Disp ose();
>>
>> ' trigger onpaint
>> Invalidate()
>> End Sub
>>
>> Sub Page1_paint
>> If ( Not bm Is Nothing ) Then
>> e.Graphics.Draw ImageUnscaled(b m, 0, 0, 0, 0, 0 )
>> End If
>> End Sub
>>
>> Sub Page1_Closing
>> bm.Dispose
>> bm = Nothing
>> End Sub
>>
>> HTH,
>> Greetings
>>
>>[color=darkred]
>> >
>> > Any thoughts here? Maybe this cannot be done in VB.
>> >
>> > Hamil.
>> >[/color]
>>
>>
>>[/color][/color]

Re: A paint event question

Hi,

<snipped>
[color=blue][color=green]
>> It seems to me that there should be some way to scale, interpolate, and
>> draw
>> the image to a buffer that is saved. Then at the paint event, the buffer
>> could be read and drawn without having to go through the scaling and
>> interpolation every time.[/color]
>
> You can draw the Bitmap from file into a memory Bitmap and then paint the
> memory Bitmap inside onpaint, eg.:
>
> Public Filename as String
> Dim bm As Bitmap ' memory bitmap
>
> Public Sub DrawTif()
> Dim fileBitmap As Bitmap = Bitmap.FromFile (FileName)
>
> ' create memory bitmap
> Dim gfx As Graphics = CreateGraphics( )
> bm = New Bitmap( 400, 500, gfx )
> gfx.Dispose()
>
> ' draw file-bitmap scaled into memory-bitmap
> gfx = Graphics.FromIm age( bm )
> gfx.Interpolati onMode = Drawing2D.Inter polationMode.Hi ghQualityBicubi c
> gfx.DrawImage(f ileBitmap, New Rectangle(0, 0, 400, 500))
> gfx.Dispose()
>
> ' dispose file bitmap
> fileBitmap.Disp ose();
>
> ' trigger onpaint
> Invalidate()
> End Sub[/color]

Because Dennis asked something about the speed of DrawImage, i was thinking
that OnPaint could be faster if you do not draw the whole memory Bitmap but
just the invalidated part.

Sub Page1_paint
If ( Not bm Is Nothing ) Then
e.Graphics.Draw Image(bm, e.ClipRectangle , e.ClipRectangle ,
GraphicsUnit.Pi xel)
End If
End Sub

HTH,
Greetings
[color=blue]
>
> Sub Page1_Closing
> bm.Dispose
> bm = Nothing
> End Sub
>
> HTH,
> Greetings
>
>[color=green]
>>
>> Any thoughts here? Maybe this cannot be done in VB.
>>
>> Hamil.
>>[/color]
>
>[/color]

RE: A paint event question

Thanks to both of you..

Barts first suggestion was much better than the way I was doing theonPaint.
Barts second suggestion was even better.

I looked into the BitBlt approach and I think it might be even faster but I
think this method would require me operating "outside" of VB.net exclusively,
i.e. require a Win API call.
Barts second suggeston where only the required part is repainted works very
well even on my slow 1 GHz Pentium III.

Thanks again.

Hamil.








"hamil" wrote:
[color=blue]
> The following code will display a tif file on a form. When another form is
> moved over the tif image, the tif image is erased where the form was moved.
> A paint event occurs when this happens. My question is..how would I save the
> tif images as soon as it is initially painted, and then restore the image in
> a paint event. It seems to me that there should be some sort of a SaveImage
> method and a RestoreImage method that would be fast. Note: Page1 is the form
> name, and FileName is passed from a routine on another form.
>
> Public Filename as string
> dim gr as graphics
>
> Public Sub DrawTif()
> Dim bm As Bitmap
>
> bm = Bitmap.FromFile (FileName)
>
> gr = Me.CreateGraphi cs
> gr.Interpolatio nMode = Drawing2D.Inter polationMode.Hi ghQualityBicubi c
> gr.DrawImage(bm , New Rectangle(0, 0, 400, 500))[color=green][color=darkred]
> >>> can I save the image here[/color][/color]
> End Sub
>
> sub Page1_paint[color=green][color=darkred]
> >>>>> and restore it here[/color][/color]
> end sub
>
> sub Page1_Closing
> gr.dispose
> end sub[/color]