How do you generate an RGBA image in Core Graphics?

Question

I\'m trying to generate an RGBA8 image from text to use as an OpenGL ES 2.0 texture.

+(UIImage *)imageFromText:(NSString *)text
{
  UIFont *font = [UIFont sy         


        

Answer 1

The color space you specify during creation wouldn't cause an error like that.

The reason you're getting that error is that you've specified 8 bits per component, presumably 4 color components in the 4*size.width value you passed in for bytesPerRow, yet a bitmapInfo parameter of kCGImageAlphaNone. kCGImageAlphaNone means only RGB, not RGBA. If you want RGBA, you should most likely specify kCGImageAlphaLast kCGImageAlphaPremultipliedLast.

[EDIT] sorry. I should have said kCGImageAlphaPremultipliedLast, not kCGImageAlphaLast.

So, something like this:

CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
CGContextRef contextRef =  CGBitmapContextCreate(NULL,
                                                 size.width,
                                                 size.height,
                                                 8,
                                                 4 * size.width,
                                                 colorSpace,
                                                 kCGImageAlphaPremultipliedLast);