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3. Portable Network Graphics (PNG)

Png NeuQuant Example

PNG Indexed format Format Conversion

Saves image to PNG format using different bitness, color quantization and dithering algorithms.

Сode Snippet

public static void Run()
{
    Save("Chicago.jpg");
    Save("Stamp.png");
}

private static void Save(string sourceFileName)
{
    // Source file information
    long sourceFileSize = new System.IO.FileInfo(sourceFileName).Length;

    Console.WriteLine("Source file:");
    Console.WriteLine("  {0}", sourceFileName);
    Console.WriteLine("  {0:f2} KB", sourceFileSize / 1024f);

    var baseName = System.IO.Path.GetFileNameWithoutExtension(sourceFileName);

    // Convert to 24-bit PNG
    {
        var png24bitFileName = baseName + "_24bit.png";

        // Save to PNG
        using (var bitmap = new Bitmap(sourceFileName))
        {
            bitmap.Save(png24bitFileName, new PngSettings(true));
        }

        long png24bitFileSize = new System.IO.FileInfo(png24bitFileName).Length;

        Console.WriteLine("PNG 24-bit:");
        Console.WriteLine("  {0}", png24bitFileName);
        Console.WriteLine("  {0:f2} KB ({1:f2}%)", (float)png24bitFileSize / 1024f, (float)png24bitFileSize / (float)sourceFileSize * 100f);
    }

    // Convert to 8-bit PNG using the Octree color quantization and Floyd–Steinberg dithering algorithms
    {
        var png8bitFileName = baseName + "_8bit.png";

        // Save to PNG
        using (var bitmap = new Bitmap(sourceFileName))
        {
            bitmap.ColorManagement.Convert(PixelFormat.Format8bppIndexed);

            bitmap.Save(png8bitFileName, new PngSettings(true));
        }

        long png8bitFileSize = new System.IO.FileInfo(png8bitFileName).Length;

        Console.WriteLine("PNG 8-bit (Octree, Floyd–Steinberg, no alpha transparency):");
        Console.WriteLine("  {0}", png8bitFileName);
        Console.WriteLine("  {0:f2} KB ({1:f2}%)", (float)png8bitFileSize / 1024f, (float)png8bitFileSize / (float)sourceFileSize * 100f);
    }

    // Convert to 8-bit PNG using the Neuquant color quantization algorithm
    {
        var png8bitNeuQuantFileName = baseName + "_8bit_NeuQuant.png";

        // Save to PNG
        using (var bitmap = new Bitmap(sourceFileName))
        {
            bitmap.ColorManagement.Palette = new ColorPalette(ColorPaletteType.NeuQuant);
            bitmap.ColorManagement.Convert(PixelFormat.Format8bppIndexed);

            bitmap.Save(png8bitNeuQuantFileName, new PngSettings(true));
        }

        long png8bitNeuQuantFileSize = new System.IO.FileInfo(png8bitNeuQuantFileName).Length;

        Console.WriteLine("PNG 8-bit (NeuQaunt, with alpha transparency):");
        Console.WriteLine("  {0}", png8bitNeuQuantFileName);
        Console.WriteLine("  {0:f2} KB ({1:f2}%)", (float)png8bitNeuQuantFileSize / 1024f, (float)png8bitNeuQuantFileSize / (float)sourceFileSize * 100f);
    }
}

Input

Chicago.jpg

Stamp.png

Output

Source file:
  Chicago.jpg
  101.28 KB
PNG 24-bit:
  Chicago_24bit.png
  535.18 KB (528.40%)
PNG 8-bit (Octree, Floyd–Steinberg, no alpha transparency):
  Chicago_8bit.png
  191.58 KB (189.16%)
PNG 8-bit (NeuQaunt, with alpha transparency):
  Chicago_8bit_NeuQuant.png
  204.09 KB (201.50%)
Source file:
  Stamp.png
  225.84 KB
PNG 24-bit:
  Stamp_24bit.png
  306.25 KB (135.60%)
PNG 8-bit (Octree, Floyd–Steinberg, no alpha transparency):
  Stamp_8bit.png
  72.90 KB (32.28%)
PNG 8-bit (NeuQaunt, with alpha transparency):
  Stamp_8bit_NeuQuant.png
  90.76 KB (40.19%)

Chicago_24bit.png

Chicago_8bit.png

Chicago_8bit_NeuQuant.png

Stamp_24bit.png

Stamp_8bit.png

Stamp_8bit_NeuQuant.png

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