Image cropping C# without .net library

Question

Can anyone advise on how to crop an image, let's say jpeg, without using any .NET framework constructs, just raw bytes? Since this is the only* way in Silverlight...

Or point to a library?

I'm not concerned with rendering i'm wanting to manipulate a jpg before uploading.

*There are no GDI+(System.Drawing) or WPF(System.Windows.Media.Imaging) libraries available in Silverlight.

Lockbits requires GDI+, clarified question

Using fjcore: http://code.google.com/p/fjcore/ to resize but no way to crop :(

Lou Franco Lou Franco · Accepted Answer · 2008-09-18T22:31:43

You could easily write crop yourself in fjcore. Start with the code for Resizer

http://web.archive.org/web/20140304090029/http://code.google.com:80/p/fjcore/source/browse/trunk/FJCore/Resize/ImageResizer.cs?

and FilterNNResize -- you can see how the image data is stored -- it's just simple arrays of pixels.

The important part is:

for (int y = 0; y < _newHeight; y++)
{
    i_sY = (int)sY; sX = 0;

    UpdateProgress((double)y / _newHeight);

    for (int x = 0; x < _newWidth; x++)
    {
        i_sX = (int)sX;

        _destinationData[0][x, y] = _sourceData[0][i_sX, i_sY];

        if (_color) {

            _destinationData[1][x, y] = _sourceData[1][i_sX, i_sY];
            _destinationData[2][x, y] = _sourceData[2][i_sX, i_sY];
        }

        sX += xStep;
    }
    sY += yStep;
}

shows you that the data is stored in an array of color planes (1 element for 8bpp gray, 3 elements for color) and each element has a 2-D array of bytes (x, y) for the image.

You just need to loop through the destination pixels, copying then from the appropriate place in the source.

edit: don't forget to provide the patch to the author of fjcore

Image cropping C# without .net library

4 Answers