/// <summary>
/// Converts a bitmap to a 2-bit grayscale array.
/// </summary>
/// <param name="bmp">Source bitmap</param>
/// <param name="lum">Multiply luminosity</param>
/// <param name="hue">Detected hue</param>
/// <returns>Array with value for every pixel between 0 and 3</returns>
public static byte[] ConvertToGray2(BitmapSource bmp, double lum, out double hue)
{
var frame = new byte[bmp.PixelWidth * bmp.PixelHeight];
var bytesPerPixel = (bmp.Format.BitsPerPixel + 7) / 8;
var bytes = new byte[bytesPerPixel];
var rect = new Int32Rect(0, 0, 1, 1);
double imageHue = 0;
for (var y = 0; y < bmp.PixelHeight; y++)
{
rect.Y = y;
for (var x = 0; x < bmp.PixelWidth; x++)
{
rect.X = x;
bmp.CopyPixels(rect, bytes, bytesPerPixel, 0);
// convert to HSL
double h;
double saturation;
double luminosity;
ColorUtil.RgbToHsl(bytes[2], bytes[1], bytes[0], out h, out saturation, out luminosity);
frame[y * bmp.PixelWidth + x] = (byte)Math.Round(Math.Min(1, luminosity * lum) * 3d);
if (luminosity > 0)
{
imageHue = h;
}
}
}
hue = imageHue;
return(frame);
}
/// <summary>
/// Converts a bitmap to an RGB24 array.
/// </summary>
/// <param name="bmp">Source bitmap</param>
/// <param name="buffer">Destination buffer. Will be filled with RGB values for each pixel between 0 and 255.</param>
/// <param name="offset">Offset in destination array</param>
/// <param name="lum">Multiply luminosity</param>
public static void ConvertToRgb24(BitmapSource bmp, byte[] buffer, int offset = 0, double lum = 1)
{
var bytesPerPixel = (bmp.Format.BitsPerPixel + 7) / 8;
var bytes = new byte[bytesPerPixel];
var rect = new Int32Rect(0, 0, 1, 1);
var pos = offset;
for (var y = 0; y < bmp.PixelHeight; y++)
{
for (var x = 0; x < bmp.PixelWidth; x++)
{
rect.X = x;
rect.Y = y;
bmp.CopyPixels(rect, bytes, bytesPerPixel, 0);
if (Math.Abs(lum - 1) > 0.01)
{
double hue, saturation, luminosity;
byte r, g, b;
ColorUtil.RgbToHsl(bytes[2], bytes[1], bytes[0], out hue, out saturation, out luminosity);
ColorUtil.HslToRgb(hue, saturation, luminosity * lum, out r, out g, out b);
buffer[pos] = r;
buffer[pos + 1] = g;
buffer[pos + 2] = b;
}
else
{
buffer[pos] = bytes[2]; // r
buffer[pos + 1] = bytes[1]; // g
buffer[pos + 2] = bytes[0]; // b
}
pos += 3;
}
}
}
/// <summary>
/// Converts an RGB24 frame to a grayscale array.
/// </summary>
/// <param name="width">Width in pixels</param>
/// <param name="height">Height in pixels</param>
/// <param name="frameRgb24">RGB24 frame, top left to bottom right, three bytes per pixel with values between 0 and 255</param>
/// <param name="numColors">Number of gray tones. 4 for 2 bit, 16 for 4 bit</param>
/// <returns>Gray2 frame, top left to bottom right, one byte per pixel with values between 0 and 3</returns>
public static byte[] ConvertToGray(int width, int height, byte[] frameRgb24, int numColors)
{
var frame = new byte[width * height];
var pos = 0;
for (var y = 0; y < height; y++)
{
for (var x = 0; x < width * 3; x += 3)
{
var rgbPos = y * width * 3 + x;
// convert to HSL
double hue;
double saturation;
double luminosity;
ColorUtil.RgbToHsl(frameRgb24[rgbPos], frameRgb24[rgbPos + 1], frameRgb24[rgbPos + 2], out hue, out saturation, out luminosity);
frame[pos++] = (byte)Math.Round(luminosity * (numColors - 1));
}
}
return(frame);
}
/// <summary>
/// Converts a bitmap to an RGB24 array.
/// </summary>
/// <param name="bmp">Source bitmap</param>
/// <param name="buffer">Destination buffer. Will be filled with RGB values for each pixel between 0 and 255.</param>
/// <param name="offset">Offset in destination array</param>
/// <param name="lum">Multiply luminosity</param>
public static void ConvertToRgb24(BitmapSource bmp, byte[] buffer, int offset = 0, double lum = 1)
{
var stride = bmp.PixelWidth * (bmp.Format.BitsPerPixel / 8);
var bytes = new byte[bmp.PixelHeight * stride];
bmp.CopyPixels(bytes, stride, 0);
if (Math.Abs(lum - 1) > 0.01)
{
for (var i = 0; i < bytes.Length; i += 3)
{
double hue, saturation, luminosity;
byte r, g, b;
ColorUtil.RgbToHsl(bytes[i + 2], bytes[i + 1], bytes[i], out hue, out saturation, out luminosity);
ColorUtil.HslToRgb(hue, saturation, luminosity * lum, out r, out g, out b);
buffer[i] = r;
buffer[i + 1] = g;
buffer[i + 2] = b;
}
}
else
{
unsafe
{
fixed(byte *pBuffer = buffer, pBytes = bytes)
{
byte *pB = pBuffer, pEnd = pBytes + bytes.Length;
for (var pByte = pBytes; pByte < pEnd; pByte += 4, pB += 3)
{
*(pB) = *(pByte + 2);
*(pB + 1) = *(pByte + 1);
*(pB + 2) = *(pByte);
}
}
}
}
}
/// <summary>
/// Converts a bitmap to a 2-bit grayscale array by using the luminosity of the pixels and
/// histogram stretching.
/// </summary>
/// <param name="bmp">Source bitmap</param>
/// <param name="minLum">Min threshold for luminosity histogram stretching</param>
/// <param name="maxLum">Max threshold for luminosity histogram stretching</param>
/// <param name="hue">Detected hue</param>
/// <returns>Array with value for every pixel between 0 and 3</returns>
public static byte[] ConvertToGray2(BitmapSource bmp, double minLum, double maxLum, out double hue)
{
var frame = new byte[bmp.PixelWidth * bmp.PixelHeight];
var bytesPerPixel = (bmp.Format.BitsPerPixel + 7) / 8;
var bytes = new byte[bytesPerPixel];
var rect = new Int32Rect(0, 0, 1, 1);
double imageHue = 0;
for (var y = 0; y < bmp.PixelHeight; y++)
{
rect.Y = y;
for (var x = 0; x < bmp.PixelWidth; x++)
{
rect.X = x;
bmp.CopyPixels(rect, bytes, bytesPerPixel, 0);
// convert to HSL
double h;
double saturation;
double luminosity;
ColorUtil.RgbToHsl(bytes[2], bytes[1], bytes[0], out h, out saturation, out luminosity);
var pixelBrightness = (luminosity - minLum) / (maxLum - minLum);
byte frameVal = (byte)Math.Min(Math.Max(Math.Round(pixelBrightness * 3d), 0), 3);
frame[y * bmp.PixelWidth + x] = frameVal;
// Don't use very low luminosity values to calculate hue because they are less accurate.
if (frameVal > 0)
{
imageHue = h;
}
}
}
hue = imageHue;
return(frame);
}
