How do I apply multiple color masks using CGImageCreateWithMaskingColors?
I'm a bit new to objective-c and even newer at programming with Quartz 2D, so apologies in advance! I've got a method where I would like to remove a handful of specific colors (not just one) from a UIImage.
When I run my project with just one color mask being applied, it works beautifully. Once I try stacking them, the 'whiteRef' comes out NULL. I've even tried modifying my method to take a color mask and then simply ran my method twice -feeding in the different colors masks- but still no go.
Any help with this is greatly appreciated!
- (UIImage *)doctorTheImage:(UIImage *)originalImage
{
const float brownsMask[6] = {124, 255, 68, 222, 0, 165};
const float whiteMask[6] = {255, 255, 255, 255, 255, 255};
UIImageView *imageView = [[UIImageView alloc] initWith开发者_开发百科Image:originalImage];
UIGraphicsBeginImageContext(originalImage.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGImageRef brownRef = CGImageCreateWithMaskingColors(imageView.image.CGImage, brownsMask);
CGImageRef whiteRef = CGImageCreateWithMaskingColors(brownRef, whiteMask);
CGContextDrawImage (context, CGRectMake(0, 0, imageView.image.size.width, imageView.image.size.height), whiteRef);
CGImageRelease(brownRef);
CGImageRelease(whiteRef);
UIImage *doctoredImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[imageView release];
return doctoredImage;
}
Well I found a good work around! Basically, I was ultimately using the image data over a MKMapView, so all I needed to do was break down the image to it's pixels and from there I could mess around as a I please. It may not be the best option in terms of speed, but does the trick. Here is a sample of the code I'm now using.
//Split the images into pixels to mess with the image pixel colors individually
size_t bufferLength = gridWidth * gridHeight * 4;
unsigned char *rawData = nil;
rawData = (unsigned char *)[self convertUIImageToBitmapRGBA8:myUIImage];
grid = malloc(sizeof(float)*(bufferLength/4));
NSString *hexColor = nil;
for (int i = 0 ; i < (bufferLength); i=i+4)
{
hexColor = [NSString stringWithFormat: @"%02x%02x%02x", (int)(rawData[i + 0]),(int)(rawData[i + 1]),(int)(rawData[i + 2])];
//mess with colors how you see fit - I just detected certain colors and slapped
//that into an array of floats which I later put over my mapview much like the
//hazardmap example from apple.
if ([hexColor isEqualToString:@"ff0299"]) //pink
value = (float)11;
if ([hexColor isEqualToString:@"9933cc"]) //purple
value = (float)12;
//etc...
grid[i/4] = value;
}
I also borrowed some methods (ie: convertUIImageToBitmapRGBA8) from here: https://gist.github.com/739132
Hope this helps someone out!
精彩评论