Opengl-es 1.1灰度FBO

Question

我有FBO，我只是將它加載到紋理和正交（2D）網格。 我如何灰度下我的FBO紋理？

Answer 1

蘋果使用下面的OpenGL ES 1.1代碼轉換的圖像中的灰度其GLImageProcessing sample：

static void greyscale(V2fT2f *quad, float t) // t = 1 for standard perceptual weighting 
{ 
    GLfloat lerp[4] = { 1.0, 1.0, 1.0, 0.5 }; 
    GLfloat avrg[4] = { .667, .667, .667, 0.5 }; // average 
    GLfloat prcp[4] = { .646, .794, .557, 0.5 }; // perceptual NTSC 
    GLfloat dot3[4] = { prcp[0]*t+avrg[0]*(1-t), prcp[1]*t+avrg[1]*(1-t), prcp[2]*t+avrg[2]*(1-t), 0.5 }; 

    // One pass using two units: 
    // Unit 0 scales and biases into [0.5..1.0] 
    // Unit 1 dot products with perceptual weights 

    glVertexPointer (2, GL_FLOAT, sizeof(V2fT2f), &quad[0].x); 
    glTexCoordPointer(2, GL_FLOAT, sizeof(V2fT2f), &quad[0].s); 
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE); 
    glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB,  GL_INTERPOLATE); 
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_RGB,   GL_TEXTURE); 
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC1_RGB,   GL_CONSTANT); 
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC2_RGB,   GL_CONSTANT); 
    glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_ALPHA, GL_REPLACE); 
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_ALPHA,  GL_TEXTURE); 
    glTexEnvfv(GL_TEXTURE_ENV,GL_TEXTURE_ENV_COLOR, lerp); 

    // Note: we prefer to dot product with primary color, because 
    // the constant color is stored in limited precision on MBX 
    glActiveTexture(GL_TEXTURE1); 
    glEnable(GL_TEXTURE_2D); 
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE); 
    glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB,  GL_DOT3_RGB); 
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_RGB,   GL_PREVIOUS); 
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC1_RGB,   GL_PRIMARY_COLOR); 
    glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_ALPHA, GL_REPLACE); 
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_ALPHA,  GL_PREVIOUS); 

    glColor4f(dot3[0], dot3[1], dot3[2], dot3[3]); 
    validateTexEnv(); 
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); 

    // Restore state 
    glDisable(GL_TEXTURE_2D); 
    glActiveTexture(GL_TEXTURE0); 
} 

我已經完全現在放棄了1.1，特別是用於圖像處理，但灰度轉換的一個很少有效果可以在1.1中使用。