c#graphicscolormatrix
Is it possible to change hue, saturation, brightness and transparency of a Bitmap with a single ColorMatrix?
I would like to be able to change the hue, saturation, brightness and transparency with a single redraw of a Bitmap. I currently have this function (adapted from this answer: https://stackoverflow.com/a/14384449/9852011), which adjusts the saturation, brightness and transparency of an Image passed into it and it works.:
public static void AdjustImageAttributes(Image image, float brightness, float saturation, float transparency)
{
//adapted from https://stackoverflow.com/a/14384449/9852011
// Luminance vector for linear RGB
const float rwgt = 0.3086f;
const float gwgt = 0.6094f;
const float bwgt = 0.0820f;
// Create a new color matrix
ColorMatrix colorMatrix = new ColorMatrix();
// Adjust saturation
float baseSat = 1.0f - saturation;
colorMatrix[0, 0] = baseSat * rwgt + saturation;
colorMatrix[0, 1] = baseSat * rwgt;
colorMatrix[0, 2] = baseSat * rwgt;
colorMatrix[1, 0] = baseSat * gwgt;
colorMatrix[1, 1] = baseSat * gwgt + saturation;
colorMatrix[1, 2] = baseSat * gwgt;
colorMatrix[2, 0] = baseSat * bwgt;
colorMatrix[2, 1] = baseSat * bwgt;
colorMatrix[2, 2] = baseSat * bwgt + saturation;
// Adjust brightness
float adjustedBrightness = brightness - 1f;
colorMatrix[4, 0] = adjustedBrightness;
colorMatrix[4, 1] = adjustedBrightness;
colorMatrix[4, 2] = adjustedBrightness;
colorMatrix[3, 3] = transparency;
// Create image attributes
ImageAttributes imageAttributes = new ImageAttributes();
imageAttributes.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
// Draw the image with the new color matrix
using (Graphics g = Graphics.FromImage(image))
{
g.DrawImage(image, new Rectangle(0, 0, image.Width, image.Height),
0, 0, image.Width, image.Height,
GraphicsUnit.Pixel, imageAttributes);
}
}
I also found this function here: https://stackoverflow.com/a/37995434/9852011
which returns a ColorMatrix with the desired hue rotation.
ColorMatrix GetHueShiftColorMax(Single hueShiftDegrees)
{
/* Return the matrix
A00 A01 A02 0 0
A10 A11 A12 0 0
A20 A21 A22 0 0
0 0 0 1 0
0 0 0 0 1
*/
Single theta = hueShiftDegrees/360 * 2*pi; //Degrees --> Radians
Single c = cos(theta);
Single s = sin(theta);
Single A00 = 0.213 + 0.787*c - 0.213*s;
Single A01 = 0.213 - 0.213*c + 0.413*s;
Single A02 = 0.213 - 0.213*c - 0.787*s;
Single A10 = 0.715 - 0.715*c - 0.715*s;
Single A11 = 0.715 + 0.285*c + 0.140*s;
Single A12 = 0.715 - 0.715*c + 0.715*s;
Single A20 = 0.072 - 0.072*c + 0.928*s;
Single A21 = 0.072 - 0.072*c - 0.283*s;
Single A22 = 0.072 + 0.928*c + 0.072*s;
ColorMatrix cm = new ColorMatrix(
( A00, A01, A02, 0, 0 ),
( A10, A11, A12, 0, 0 ),
( A20, A21, A22, 0, 0 ),
( 0, 0, 0, 0, 0 ),
( 0, 0, 0, 0, 1 )
)
return cm;
}
So now I basically have two color matrices. What I could do is redraw the Image with the first function and then create another, similar function just for the hue and redraw it again. However, this seems unnecessary to me. I feel like there should be a way to combine the 2 matrices into 1 and do everything with just one redraw. The math in these functions is unfortunately way over my head so I have no idea where to even start.
Solution
Thanks to @JonasH who pointed me in the right direction. The answer is indeed to simply multiply the matrices. Using this information, I was able to create this class which does exactly what I wanted:
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace BIUK9000
{
public class HSBTAdjuster
{
//Hue 0 - 360, 0 is no change
//Saturation 1 is no change, <1 for decrease, >1 for increase
//Brightness 1 is no change, <1 for decrease, >1 for increase
//Transparency 1 is fully opaque, <1 for transparency
public static Bitmap HSBTAdjustedBitmap(Bitmap bitmap, float hue, float saturation, float brightness, float transparency)
{
ImageAttributes imageAttributes = HSBTAdjustedImageAttributes(hue, saturation, brightness, transparency);
Bitmap result = new Bitmap(bitmap.Width, bitmap.Height);
using Graphics g = Graphics.FromImage(result);
g.DrawImage(bitmap,
new Rectangle(0,0, bitmap.Width, bitmap.Height),
0, 0, bitmap.Width, bitmap.Height,
GraphicsUnit.Pixel, imageAttributes);
return result;
}
public static ImageAttributes HSBTAdjustedImageAttributes(float hue, float saturation, float brightness, float transparency)
{
ImageAttributes ia = new ImageAttributes();
ia.SetColorMatrix(
MultipliedColorMatrix(
SBTShiftedColorMatrix(saturation, brightness, transparency),
HueRotatedColorMatrix(hue)),
ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
return ia;
}
private static ColorMatrix MultipliedColorMatrix(ColorMatrix sbtCm, ColorMatrix hCm)
{
ColorMatrix result = new ColorMatrix();
for (int i = 0; i < 5; i++)
{
for (int j = 0; j < 5; j++)
{
result[i, j] = sbtCm[i, 0] * hCm[0, j];
result[i, j] += sbtCm[i, 1] * hCm[1, j];
result[i, j] += sbtCm[i, 2] * hCm[2, j];
result[i, j] += sbtCm[i, 3] * hCm[3, j];
result[i, j] += sbtCm[i, 4] * hCm[4, j];
}
}
return result;
}
private static ColorMatrix SBTShiftedColorMatrix(float saturation, float brightness, float transparency)
{
//adapted from https://stackoverflow.com/a/14384449/9852011
// Luminance vector for linear RGB
const float rwgt = 0.3086f;
const float gwgt = 0.6094f;
const float bwgt = 0.0820f;
// Create a new color matrix
ColorMatrix colorMatrix = new ColorMatrix();
// Adjust saturation
float baseSat = 1.0f - saturation;
colorMatrix[0, 0] = baseSat * rwgt + saturation;
colorMatrix[0, 1] = baseSat * rwgt;
colorMatrix[0, 2] = baseSat * rwgt;
colorMatrix[1, 0] = baseSat * gwgt;
colorMatrix[1, 1] = baseSat * gwgt + saturation;
colorMatrix[1, 2] = baseSat * gwgt;
colorMatrix[2, 0] = baseSat * bwgt;
colorMatrix[2, 1] = baseSat * bwgt;
colorMatrix[2, 2] = baseSat * bwgt + saturation;
// Adjust brightness
float adjustedBrightness = brightness - 1f;
colorMatrix[4, 0] = adjustedBrightness;
colorMatrix[4, 1] = adjustedBrightness;
colorMatrix[4, 2] = adjustedBrightness;
colorMatrix[3, 3] = transparency;
return colorMatrix;
}
private static ColorMatrix HueRotatedColorMatrix(float hueShiftDegrees)
{
float theta = (float)(hueShiftDegrees / 360 * 2 * Math.PI); //Degrees --> Radians
float c = (float)Math.Cos(theta);
float s = (float)Math.Sin(theta);
float A00 = (float)(0.213 + 0.787 * c - 0.213 * s);
float A01 = (float)(0.213 - 0.213 * c + 0.413 * s);
float A02 = (float)(0.213 - 0.213 * c - 0.787 * s);
float A10 = (float)(0.715 - 0.715 * c - 0.715 * s);
float A11 = (float)(0.715 + 0.285 * c + 0.140 * s);
float A12 = (float)(0.715 - 0.715 * c + 0.715 * s);
float A20 = (float)(0.072 - 0.072 * c + 0.928 * s);
float A21 = (float)(0.072 - 0.072 * c - 0.283 * s);
float A22 = (float)(0.072 + 0.928 * c + 0.072 * s);
ColorMatrix cm = new ColorMatrix();
cm.Matrix00 = A00;
cm.Matrix01 = A01;
cm.Matrix02 = A02;
cm.Matrix10 = A10;
cm.Matrix11 = A11;
cm.Matrix12 = A12;
cm.Matrix20 = A20;
cm.Matrix21 = A21;
cm.Matrix22 = A22;
cm.Matrix44 = 1;
cm.Matrix33 = 1;
return cm;
}
}
}
The HSBTAdjustedBitmap method returns the bitmap passed into it with the hue, saturation, brightness and transparency adjusted by the passed arguments.
Example of HSB being shifted with this class:
