用颜色填充CGBitmapContext

Question

I'm trying to fill a CGBitmapContext with a solid red color and get CGImgRef, but image is all transparent. Here's the code

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL,
                                             1,
                                             1,
                                             8,
                                             0,
                                             colorSpace,
                                             kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGFloat components[] = {1.0,0.0,0.0,1.0};
CGContextSetFillColor(context, components);
CGContextFillRect(context, CGRectMake(0, 0, 1, 1));
CGImageRef imgRef = CGBitmapContextCreateImage(context);

Please don't recommend using UIBezierPaths and other UIKit things. I need to use CoreGraphics.

Answer 1

The problem is that you forgot to set a fill color space. You must do that in order for CGContextSetFillColor to work correctly (because that tells it how many components to expect and how to interpret them). This works:

CGFloat components[] = {1,0,0,1};
CGContextSetFillColorSpace(context, colorSpace); // <-- this was missing
CGContextSetFillColor(context, components);
// and now fill ...

Answer 2

problem was solved using CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor) ; Btw, it would be interesting to know what i was doing wrong. Also Apple documentation on CGContextSetFillColor says "Note that the preferred API to use is now CGContextSetFillColorWithColor."