Serge's World

One of the most striking effects to apply to an image is embossing. This is effect is a form of edge-detection, and is also done using convolution, which you can read more about on my post on smoothing using convolution.

The convolution grid we use in embossing is a little different to the others we have looked at so far. It has an offset of 127, and a fixed factor of 4. The offset makes the the image appear on average as a medium gray.

The grid we will use then is

public void ApplyEmboss(double weight)
{
    ConvolutionMatrix matrix = new ConvolutionMatrix(3);
    matrix.SetAll(1);
    matrix.Matrix[0, 0] = -1;
    matrix.Matrix[1, 0] = 0;
    matrix.Matrix[2, 0] = -1;
    matrix.Matrix[0, 1] = 0;
    matrix.Matrix[1, 1] = weight;
    matrix.Matrix[2, 1] = 0;
    matrix.Matrix[0, 2] = -1;
    matrix.Matrix[1, 2] = 0;
    matrix.Matrix[2, 2] = -1;
    matrix.Factor = 4;
    matrix.Offset = 127;
    bitmapImage = Convolution3x3(bitmapImage, matrix);

}

The full source used in the series is available from https://github.com/sjmeunier/image-processor.

Originally posted on my old blog, Smoky Cogs, on 19 Nov 2009