oc 提取图片中的颜色

一、下载地址

二、 效果

三、关键代码

//获取图片某一点的颜色
- (UIColor *)colorAtPixel:(CGPoint)point {
if (!CGRectContainsPoint(CGRectMake(0.0f, 0.0f, self.image.size.width, self.image.size.height), point)) {
return nil;
}

NSInteger pointX = trunc(point.x);
NSInteger pointY = trunc(point.y);
CGImageRef cgImage = self.image.CGImage;
NSUInteger width = self.image.size.width;
NSUInteger height = self.image.size.height;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
int bytesPerPixel = 4;
int bytesPerRow = bytesPerPixel * 1;
NSUInteger bitsPerComponent = 8;
unsigned char pixelData[4] = { 0, 0, 0, 0 };
CGContextRef context = CGBitmapContextCreate(pixelData,
1,
1,
bitsPerComponent,
bytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedLast |     kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
CGContextSetBlendMode(context, kCGBlendModeCopy);

CGContextTranslateCTM(context, -pointX, pointY-(CGFloat)height);
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, (CGFloat)width, (CGFloat)height), cgImage);
CGContextRelease(context);

CGFloat red   = (CGFloat)pixelData[0] / 255.0f;
CGFloat green = (CGFloat)pixelData[1] / 255.0f;
CGFloat blue  = (CGFloat)pixelData[2] / 255.0f;
CGFloat alpha = (CGFloat)pixelData[3] / 255.0f;
NSLog(@"%f %f %f %f",(CGFloat)pixelData[0],(CGFloat)pixelData[1],(CGFloat)pixelData[2],(CGFloat)pixelData[3]);
return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}