Flip image vertically in Compact Framework

[shailendrab]

Hi,

I have been trying to flip an image vertically before saving in disk in AVI format. I really dont know why i need to flip it first before saving, any idea?

To do this currently i am performing a simple algorithm...

        public Bitmap RotateFlip(Bitmap source, RotateFlipType change)
        {
            Bitmap dest = new Bitmap(source.Size.Width, source.Size.Height);
            int MaxWidthIndex = source.Size.Width - 1;
            int MaxHeightIndex = source.Size.Height - 1;

            for (int X = 0; X < source.Size.Width; X++)
            {
                for (int Y = 0; Y < source.Size.Height; Y++)
                {
                    switch (change)
                    {
                        case RotateFlipType.RotateNoneFlipY:
                            dest.SetPixel(MaxWidthIndex - X, Y, source.GetPixel(MaxWidthIndex - X, MaxHeightIndex - Y));
                            break;
                        default:
                            throw new Exception("Not implemented");
                    }
                }
            }

            return dest;
        }

This works correctly but has severe performance bottleneck. I guess due to Set & Get pixel methods.

If you know a better approach and can share code with me, I will really appreciate.

Thanks,
Shailendra

[tlhintoq]

TIP: When you are writing your question, there is a button on the tool bar that wraps the [code] tags around your copy/pasted code. It helps a bunch. Its the button with a '#' on it. More on tags. They're cool. Check'em out.

[tlhintoq]

I really dont know why i need to flip it first before saving

Then why are you doing it?

before saving in disk in AVI format.

Excuse me? You're saving your bitmap as an avi? Why?

http://msdn.microsoft.com/en-us/library/system.drawing.image.rotateflip(VS.80).aspx?ppud=4

[shailendrab]

Hi,

Thanks for reply... answers to your questions...


Then why are you doing it?

Bcoz i have to. If i dont, when i play recorded video, i see vertically flipped images being displayed.

Excuse me? You're saving your bitmap as an avi? Why?

Sorry I made an ambiguous statement. What i meant is, i am getting images from a netwrok camera and i want to record it as video. so to record video i am using AVI library (found a wrapper on code project), which allow me to add images into a video stream. However it is required to perform a flip before saving an image (this is the part i am not sure about).

I hope i m clear this time :)

Thanks
Shailendra

[GaryTexmo]

I don't know of a faster way to do a image flip than to just parse through the data and change it around. The only way I could say to optimize it would be that you could remove the switch statement in your code. Maybe set up some variables depending on the value...

destImage.SetPixel((direction * x) + startX, (direction * y) + startY);

Where direction is 1 or -1 and startX/Y is 0 or the width/height accordingly.

There may be faster ways, but unfortunately I don't know them. Sorry!

[shailendrab]

Thank you very much Gary for suggesting improvement. I will try this one.

[GaryTexmo]

Hmm, additionally it seems there's a built-in method on the Image class.

http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/a1e62e03-d732-444d-bb3d-6e7907fd5e16

I don't know if it's any faster or not though, worth a try? I can't help but wonder if you know about this though 'cause you're using the same terminology and the same enum. If it's a matter of having it on a Bitmap class vs. an Image class, I'm pretty sure you can load a bitmap into an Image and vice versa. Some googling might be in order there though.