Iphone app: how to fill image with blank areas using coregraphics?

Question

I am starting to develop applications for Iphone and wondering if the following can be done:

I have a .png image, which is a simple drawing of a shape bounded by black edges and empty areas. I wonder if there is a method or mode for filling closed empty areas of the image.

It looks like a MSpaint filling pot.

I have this code:

CGContextRef ctx = UIGraphicsGetCurrentContext(); UIImage *image = [UIImage imageNamed:@"myImage.png"]; CGContextDrawImage(context, CGRectMake(0, 0, 145, 15), image.CGImage); [image drawInRect:CGRectMake(0, 0, 145, 15)]; 

Now I do not know what to do to fill out ...

I would really appreciate it if someone could answer this question. Thank you very much!

Answer 1

I have an image ... which ... is limited by black edges and empty areas.

If by “empty” you mean that these areas have alpha zero, first fill in the context of the desired color (filling in the entire area of ​​the context), and then draw the image on top. Color will be displayed where the image is transparent, and not where it is missing.

A closer match to the request would be to draw an image in copy overlay mode, and then fill in the color in source blend mode.

Mix modes are your friend; learn them well, because you can do a lot with them.