I’m working hard on my UIKit / Quartz book, where I’m doing a lot of coverage of drawing using Bezier paths. Today, after a pretty detail-oriented day of writing, I was more than ready to take a break.

I headed over to IRC and encountered a particularly interesting challenge. It came in the form of Clarus the dog cow. She’s normally a bitmap, which isn’t something that translates particularly well into the world of UIImages. Surely, I thought, there should be a way to generalize her to a reusable path.

Inspired by my PaintCode write-up from today, I decided to create a generalized bitmap-to-Bezier path method to address this. What I ended up with is a category that transforms bytes into an easy-to-draw UIBezierPath.

@implementation UIBezierPath (BitmapExtension)
+ (UIBezierPath *) pathFromBitmap: (NSData *) data size: (CGSize) size
{
    Byte *bytes = (Byte *) data.bytes;
    CFIndex height = size.height;
    CFIndex width = size.width;

    if (height * width != data.length)
    {
        NSLog(@"Error: size does not match data's available bytes");
        return nil;
    }

    UIBezierPath *bezierPath = [UIBezierPath bezierPath];
    for (CFIndex y = 0; y < height; y++)
    {
        for (CFIndex x = 0; x < width; x++)
        {
            CFIndex index = y * width + x;
            if (bytes[index] != 0)
            {
                UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(x, y, 1, 1)];
                [bezierPath appendPath:path];
            }
        }
    }

    return bezierPath;
}