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iOS 获取图片上某一像素点的颜色

iOS 获取图片上某一像素点的颜色

作者: 瞬csr | 来源:发表于2017-02-14 09:40 被阅读1917次
       //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;
    
            return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
        }

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      • 秋燕归:你好,发现一个问题,如果UIimageview的frame是整个屏幕,而uiiamgeview的image像素过高超过了整个屏幕,这时候取出来的值是不对的

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