iPhone - copying a UIBezierPath to a CGPath and rendering as the original

Question

I have created a complex UIBezierPath that is composed of several path segments, solid, dashed, lines, colors, arcs, etc. So I have this and now I want to render it to a CGContext.

So, I convert it to a CGPathReference using

CGPathRef cgPath = CGPathCreateCopy(aBezierPath.CGPath);

The problem is this: in theory, if I want to draw a path on a CGContext, I have to define the stroke width, color, line style, blending mode, etc. for each segment that needs to be different, but the UIBezierPath I have already created contains all this information.

So, I wonder if there is a way to just to "stamp" the CGPath as it is on the CGContext, so it will be stamped with all the original information?

thanks.

Can you not just use the UIBezierPath's stroke method? – Tom Irving Jun 11 '11 at 11:45 — Tom Irving, Jun 11 '11 at 11:45

Fattie · Accepted Answer · 2014-01-28T07:45:42.190

DR, you're right: it is very confusing!

But I think Tom is correct, just use [aBezierPath stroke].

So, it would be something like this:

REF is a (CGContextRef) which you have built.

YOURBEZIERPATH is a (UIBezierPath*).

Inevitably you have to deal with the "drawing upside down" issue, so:

UIGraphicsPushContext(REF);
CGContextSaveGState(REF);
CGContextTranslateCTM(REF, 0, the height*);
CGContextScaleCTM(REF, 1.0, -1.0);
[YOURBEZIERPATH stroke];
CGContextRestoreGState(REF);
UIGraphicsPopContext();

So that's it.

Re your comment below: I have an array of UIBezierPaths. Each bezier has its own style and color.

Does this help? ... Replace the one "stroke" call, with a for loop:

UIGraphicsPushContext(REF);
CGContextSaveGState(REF);
CGContextTranslateCTM(REF, 0, the height*);
CGContextScaleCTM(REF, 1.0, -1.0);

for each of YOURBEZIERPATH in your array...
    {
    CGContextSaveGState(REF);
    [YOURBEZIERPATH stroke];
    CGContextRestoreGState(REF);
    }

CGContextRestoreGState(REF);
UIGraphicsPopContext();

You actually do not need to bother using aBezierPath.CGPath, or, a copy thereof.

Again you are right, it is very confusing, the two worlds of UI and CG !!

*the height: often something like self.frame.size.height. I just include this for anyone looking for general example code in the future.

Thanks, this almost works for me. My only problem is this: I have an array of UIBezierPaths that I have to draw to the context. Each bezier has its own style and color. When I use your method to stroke the paths in a loop, every time your method is called, all paths, including those previously stroked, changed to the last specified style. For example: I have 3 paths: dashed/blue, solid/red, solid/green. After the first run I have a dashed/blue path. After the second run, I have two solid/red paths and after the third run, all paths change to solid/green. — Duck, Jun 11 '11 at 17:33
Thanks Joe, I was mistaken a few concepts but now it is working like magic. Thanks!!! — Duck, Jun 12 '11 at 21:27
No, I did the inverse, I draw all the paths every time I need to update something. Drawing all the paths is not as slow as I thought, then it is working very well. — Duck, Jun 13 '11 at 19:22

iPhone - copying a UIBezierPath to a CGPath and rendering as the original

1 Answers1