Question

I have some C# code that is doing key-color replacement based on hue. On my local machine, it’s executing perfectly. However when I push it up to the server it replaces “some” but not all of the colors. It’s like it’s just deciding not to run part of the code.

The images are lossless PNGs – they are intact on the server. Is this some kind of threading issue? My code is not threaded here (beyond what the webserver does), but has anyone ever seen anything similar happen?

It might also help if I mention that this code is compiled in a separate library project and then referenced from an MVC3 application.

Thanks, and here is the code sample:

private void _ReplaceImageColor(Image img, Color baseColor, Color newColor)
{
    Bitmap bmp = (Bitmap)img;
    double baseHue = baseColor.GetHue();
    for (int x = 0; x < bmp.Width; x++)
    {
        for (int y = 0; y < bmp.Height; y++)
        {
            double pixelHue, pixelSat, pixelVal;
            ColorProcessor.ColorToHSV(bmp.GetPixel(x, y), out pixelHue, out pixelSat, out pixelVal);
            if (pixelHue == baseHue)
            {
                Color setColor = ColorProcessor.ColorFromHSV(newColor.GetHue(), pixelSat, pixelVal);
                bmp.SetPixel(x, y, setColor);
            }
        }
    }
}

Here’s the methods from ColorProcessor since people asked…

public static void ColorToHSV(Color color, out double hue, out double saturation, out double value)
{
    int max = Math.Max(color.R, Math.Max(color.G, color.B));
    int min = Math.Min(color.R, Math.Min(color.G, color.B));

    hue = color.GetHue();
    saturation = (max == 0) ? 0 : 1d - (1d * min / max);
    value = max / 255d;
}

public static Color ColorFromHSV(double hue, double saturation, double value)
{
    int hi = Convert.ToInt32(Math.Floor(hue / 60)) % 6;
    double f = hue / 60 - Math.Floor(hue / 60);

    value = value * 255;
    int v = Convert.ToInt32(Math.Max(value, 0));
    int p = Convert.ToInt32(Math.Max(value * (1 - saturation), 0));
    int q = Convert.ToInt32(Math.Max(value * (1 - f * saturation), 0));
    int t = Convert.ToInt32(Math.Max(value * (1 - (1 - f) * saturation), 0));

    if (hi == 0)
        return Color.FromArgb(255, v, t, p);
    else if (hi == 1)
        return Color.FromArgb(255, q, v, p);
    else if (hi == 2)
        return Color.FromArgb(255, p, v, t);
    else if (hi == 3)
        return Color.FromArgb(255, p, q, v);
    else if (hi == 4)
        return Color.FromArgb(255, t, p, v);
    else
        return Color.FromArgb(255, v, p, q);
}

Answer 1

You might want to check very carefully that your dll references are the same on the server as on the dev machine. Hanselman had an article on that very thing recently: Confirm Your Expectations and Version Numbers in Production Environments

Also, since it is behaving differently on debug versus release mode check that it is using the same bitness in the build to eliminate that potential variation (e.g. x86) which can manifest on floating point numbers.