OSX Xcode：用指定的RGB颜色预填充位图吗？

Question

Is there a method for filling a bitmap (context) with a specified RGB color?

Here is the procedure that I have implemented:

1. allocate memory for bitmap (malloc)
2. memset allocated memory with zeros (to get a black background)

3. Create CGContextRef:

   CGContextRef ctx = CGBitmapContextCreate(memData, width, height,8,bytesPerRow,colorSpace,bmpInfo)

4. Insert image:

   CGContextDrawImage(ctx, CGRectMake(x,y,imgWidth, imgHeight), anotherImg)

5. Finalize image:

   CGImageRef createdImg = CGBitmapContextCreateImage(context)

As you can see from the above, the background will always be black. I want to be able to select an RGB color for the background. How is that done?

This is for an OSX app in XCode.

My functions are implemented in C as I'm not too comfortable with the Objective C syntax.

Answer 1

Set the fill colour ( CGContextSetFillColorWithColor ) and then fill the whole context ( CGContextFillRect ).

Also, you might want to consider passing NULL as the data parameter to CGBitmapContextCreate so that you don't need to worry about the memory management for it.