How can I read a pixel's color from a BitmapImage in Silverlight?

Question

I have a BitmapImage instance in Silverlight, and I am trying to find a way to read the color information of each pixel in the image. How can I do this? I see that there is a CopyPixels() method on this class that writes pixel information into the array that you pass it, but I don't know how to read color information out of that array.

How can I do this?

Answer 1

This is not possible with the current Bitmap API in the currently released Silverlight 3 beta.

The Silverlight BitmapImage file does not have a CopyPixels method. Please see the MSDN documentation here.

Answer 2

Look for the WriteableBitmap class in Silverlight 3. This class has a member Pixels which returns the bitmap's pixel data in an array of int's.

An example with a transform. bi is an BitmapImage object.

Image img = new Image();
img.source = bi;

img.Measure(new Size(100, 100));
img.Arrange(new Rect(0, 0, 100, 100));

ScaleTransform scaleTrans = new ScaleTransform();
double scale = (double)500 / (double)Math.Max(bi.PixelHeight, bi.PixelWidth);
scaleTrans.CenterX = 0;
scaleTrans.CenterY = 0;
scaleTrans.ScaleX = scale;
scaleTrans.ScaleY = scale;

WriteableBitmap writeableBitmap = new WriteableBitmap(500, 500);
writeableBitmap.Render(img, scaleTrans);

int[] pixelData = writeableBitmap.Pixels;