RGB rotation

shader/hue.frag

@@ -1,48 +1,12 @@
 
-uniform sampler2D inputTexture;
-uniform float hueAdjust;
+uniform sampler2D texture;
+uniform lowp mat3 rotationMat;
 
 varying vec2 v_texCoord;
 
 void main ()
 {
-	const vec4  kRGBToYPrime = vec4 (0.299, 0.587, 0.114, 0.0);
-	const vec4  kRGBToI      = vec4 (0.596, -0.275, -0.321, 0.0);
-	const vec4  kRGBToQ      = vec4 (0.212, -0.523, 0.311, 0.0);
+	vec4 color = texture2D (texture, v_texCoord.xy);
 
-	const vec4  kYIQToR      = vec4 (1.0, 0.956, 0.621, 0.0);
-	const vec4  kYIQToG      = vec4 (1.0, -0.272, -0.647, 0.0);
-	const vec4  kYIQToB      = vec4 (1.0, -1.107, 1.704, 0.0);
-
-	/* Sample the input pixel */
-	vec4    color   = texture2D (inputTexture, v_texCoord.xy);
-
-	/* Convert to YIQ */
-	float   YPrime  = dot (color, kRGBToYPrime);
-	float   I       = dot (color, kRGBToI);
-	float   Q       = dot (color, kRGBToQ);
-
-	/* Calculate the hue and chroma */
-	float   hue     = atan (Q, I);
-	float   chroma  = sqrt (I * I + Q * Q);
-
-	/* Make the user's adjustments */
-	hue += hueAdjust;
-
-	/* Remember old I and color */
-	float IOriginal = I;
-	vec4 coOriginal = color;
-
-	/* Convert back to YIQ */
-	Q = chroma * sin (hue);
-	I = chroma * cos (hue);
-
-	/* Convert back to RGB */
-	vec4 yIQ = vec4 (YPrime, I, Q, 0.0);
-	color.r  = dot  (yIQ, kYIQToR);
-	color.g  = dot  (yIQ, kYIQToG);
-	color.b  = dot  (yIQ, kYIQToB);
-
-	/* Save the result */
-	gl_FragColor = (IOriginal == 0.0) ? coOriginal : color;
+	gl_FragColor = vec4(rotationMat * color.rgb, color.a);
 }

src/bitmap.cpp

@@ -29,6 +29,8 @@
 
 #include <pixman.h>
 
+#include <math.h>
+
 #include "gl-util.h"
 #include "gl-meta.h"
 #include "quad.h"
@@ -854,13 +856,28 @@ void Bitmap::hueChange(int hue)
 	quad.setTexPosRect(texRect, texRect);
 	quad.setColor(Vec4(1, 1, 1, 1));
 
-	/* Calculate hue parameter */
+	/* Calculate hue rotation matrix */
 	hue = wrapRange(hue, 0, 359);
-	float hueAdj = -((M_PI * 2) / 360) * hue;
+	float hueRad = (M_PI / 180.0f) * hue;
+	float x = cos(hueRad);
+	float y = sin(hueRad);
+	float a = (1.0f - x) / 3.0f;
+	float b = sqrt(1.0f / 3.0f) * y;
+
+	float mat[9];
+	mat[0] = x + a;
+	mat[1] = a + b;
+	mat[2] = a - b;
+	mat[3] = mat[2];
+	mat[4] = mat[0];
+	mat[5] = mat[1];
+	mat[6] = mat[1];
+	mat[7] = mat[2];
+	mat[8] = mat[0];
 
 	HueShader &shader = shState->shaders().hue;
 	shader.bind();
-	shader.setHueAdjust(hueAdj);
+	shader.setRotationMat(mat);
 
 	FBO::bind(newTex.fbo);
 	p->pushSetViewport(shader);

src/gl-fun.h

@@ -90,6 +90,7 @@ typedef void (APIENTRYP _PFNGLUNIFORM1FPROC) (GLint location, GLfloat v0);
 typedef void (APIENTRYP _PFNGLUNIFORM2FPROC) (GLint location, GLfloat v0, GLfloat v1);
 typedef void (APIENTRYP _PFNGLUNIFORM4FPROC) (GLint location, GLfloat v0, GLfloat v1, GLfloat v2, GLfloat v3);
 typedef void (APIENTRYP _PFNGLUNIFORM1IPROC) (GLint location, GLint v0);
+typedef void (APIENTRYP _PFNGLUNIFORMMATRIX3FVPROC) (GLint location, GLsizei count, GLboolean transpose, const GLfloat* value);
 typedef void (APIENTRYP _PFNGLUNIFORMMATRIX4FVPROC) (GLint location, GLsizei count, GLboolean transpose, const GLfloat* value);
 
 /* Vertex attribute */
@@ -174,6 +175,7 @@ typedef void (APIENTRYP _PFNGLRELEASESHADERCOMPILERPROC) (void);
 	GL_FUN(Uniform2f, _PFNGLUNIFORM2FPROC) \
 	GL_FUN(Uniform4f, _PFNGLUNIFORM4FPROC) \
 	GL_FUN(Uniform1i, _PFNGLUNIFORM1IPROC) \
+	GL_FUN(UniformMatrix3fv, _PFNGLUNIFORMMATRIX3FVPROC) \
 	GL_FUN(UniformMatrix4fv, _PFNGLUNIFORMMATRIX4FVPROC) \
 	/* Vertex attribute */ \
 	GL_FUN(BindAttribLocation, _PFNGLBINDATTRIBLOCATIONPROC) \

src/shader.cpp

@@ -550,18 +550,12 @@ HueShader::HueShader()
 
 	ShaderBase::init();
 
-	GET_U(hueAdjust);
-	GET_U(inputTexture);
+	GET_U(rotationMat);
 }
 
-void HueShader::setHueAdjust(float value)
+void HueShader::setRotationMat(const float value[9])
 {
-	gl.Uniform1f(u_hueAdjust, value);
-}
-
-void HueShader::setInputTexture(TEX::ID tex)
-{
-	setTexUniform(u_inputTexture, 0, tex);
+	gl.UniformMatrix3fv(u_rotationMat, 1, GL_FALSE, value);
 }
 
 

src/shader.h

@@ -240,11 +240,10 @@ class HueShader : public ShaderBase
 public:
 	HueShader();
 
-	void setHueAdjust(float value);
-	void setInputTexture(TEX::ID tex);
+	void setRotationMat(const float value[9]);
 
 private:
-	GLint u_hueAdjust, u_inputTexture;
+	GLint u_rotationMat;
 };
 
 class SimpleMatrixShader : public ShaderBase