Question

Is it possible make a CCSprite to black and white one using setBlendFunc ? If yes please tell how to do it.

More Details:

I have to make my game sprite (background,character) to gray salce/black and white for a certain point of time. I dont want to take another image for this. I have tried CCTexture2DMutable. But the thing is it take extra memory of the same sprite.

Is there any way to use one mask image and make all sprite to gray scale.
Please help.

Answer 1

This is not mathematically correct grayscaling, but looks black & white:

// setup grayscaling:
GLfloat rgba[4] = { 0.65f, 0.65f, 0.65f, 1.0f };
glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE );
glTexEnvi( GL_TEXTURE_ENV, GL_COMBINE_RGB, GL_DOT3_RGB );
glTexEnvfv(GL_TEXTURE_ENV, GL_TEXTURE_ENV_COLOR, rgba );
glTexEnvi( GL_TEXTURE_ENV, GL_SRC0_RGB, GL_CONSTANT );
glTexEnvi( GL_TEXTURE_ENV, GL_OPERAND0_RGB, GL_SRC_COLOR );
glTexEnvi( GL_TEXTURE_ENV, GL_SRC1_RGB, GL_TEXTURE );
glTexEnvi( GL_TEXTURE_ENV, GL_OPERAND1_RGB, GL_SRC_COLOR );
// ... glDrawArrays() here ...
// turn off grayscaling:
glTexEnvi (GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

Insert this code into CCSprite drawing method. 0.65f value of rgba is set experimentally, try to tune it.