iOS开发之获取图片上点的颜色值

时间有限我们就不多说，直接上代码，这里实现使用了分类，名称大家可以随意发挥

获取图片上某个点的颜色值(不包含alpha)

XXXXXXXX.h文件

@interface UIImage (XXXXXXXX)

/// 获取图片上某个点的RGB值(不包含alpha)。
- (nullable NSArray<NSNumber *> *)pixelColorFromPoint:(CGPoint)point;

@end

XXXXXXXX.m文件

@implementation UIImage (XXXXXXXX)

/// 获取图片上某个点的颜色值(不包含alpha)。
- (nullable NSArray<NSNumber *> *)pixelColorFromPoint:(CGPoint)point {
    // 判断点是否超出图像范围
    if (!CGRectContainsPoint(CGRectMake(0, 0, self.size.width, self.size.height), point)) return nil;
    
    // 将像素绘制到一个1×1像素字节数组和位图上下文。
    NSInteger pointX = trunc(point.x);
    NSInteger pointY = trunc(point.y);
    CGImageRef cgImage = self.CGImage;
    CGFloat width = self.size.width;
    CGFloat height = self.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);
    
    // 将指定像素绘制到上下文中
    CGContextTranslateCTM(context, -pointX, pointY - height);
    CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, width, height), cgImage);
    CGContextRelease(context);
    
    CGFloat red = (CGFloat)pixelData[0];
    CGFloat green = (CGFloat)pixelData[1];
    CGFloat blue = (CGFloat)pixelData[2];
    return @[@(red), @(green), @(blue)];
}
@end

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