获取图片每（某）个像素点的RBGA值

来源：互联网发布：练英语六级听力的软件编辑：程序博客网时间：2024/06/05 20:07

最近项目有个需求，获取调色板上某个点的RBGA值，来设置背景颜色。查找了一些资料，经过多次测试，最终拿到的RGBA值基本一致（这里为什么说基本一致呢，如果RGBA值的取值范围在0～255之间的话，结果会有1-2个点的误差）。方法如下：

获取图片上某个点的RGBA值

//获取图片某个点的RGBA值- (NSMutableArray *)getImagePixel:(UIImage *)image point:(CGPoint)aPoint {        NSMutableArray *byteArray = [[NSMutableArray alloc] initWithCapacity:10];    CGImageRef cgimage = image.CGImage;    size_t scale = CGImageGetWidth(cgimage) / image.size.width;        size_t bpr = CGImageGetBytesPerRow(cgimage);             //每行的字节数    size_t bpp = CGImageGetBitsPerPixel(cgimage);            //每个像素的位数    size_t bpc = CGImageGetBitsPerComponent(cgimage);        //每个字节的组成部分    size_t bytes_per_pixel = bpp / bpc;        // Get CGDataProviderRef from cgimage    CGDataProviderRef provider = CGImageGetDataProvider(cgimage);        @autoreleasepool    {        //Using (__bridge_transfer NSData *) casts the provider to type NSData and gives ownership to ARC, but still not discarded        NSData *data = (__bridge_transfer NSData *)CGDataProviderCopyData(provider);                const UInt8 *bytes = (Byte *)[data bytes];                size_t row = aPoint.y*scale;        size_t col = aPoint.x*scale;                const UInt8* pixel = &bytes[row * bpr + col * bytes_per_pixel];                for(unsigned short i = 0; i < 4; i+=4) {                        unsigned short red = pixel[i];                  // red channel - unused            unsigned short green = pixel[i+1];              // green channel            unsigned short blue = pixel[i+2];               // blue channel            unsigned short alpha = pixel[i+3];              // alpha channel - unused                        [byteArray addObject:@(red)];            [byteArray addObject:@(green)];            [byteArray addObject:@(blue)];            [byteArray addObject:@(alpha)];        }        data = nil;    }    return byteArray;}

获取图片每个像素点的RGBA值

//获取图片每个像素点的RGBA值- (NSMutableArray *)getImagePixel:(UIImage *)image point:(CGPoint)aPoint {        // Create  array to add all files into total image    NSMutableArray *byteArray = [[NSMutableArray alloc] initWithCapacity:(image.size.width * image.size.height)];        CGImageRef cgimage = image.CGImage;        size_t width  = CGImageGetWidth(cgimage);    size_t height = CGImageGetHeight(cgimage);        size_t bpr = CGImageGetBytesPerRow(cgimage);             //每行的字节数    size_t bpp = CGImageGetBitsPerPixel(cgimage);            //每个像素的位数    size_t bpc = CGImageGetBitsPerComponent(cgimage);        //每个字节的组成部分    size_t bytes_per_pixel = bpp / bpc;        // Get CGDataProviderRef from cgimage    CGDataProviderRef provider = CGImageGetDataProvider(cgimage);        @autoreleasepool    {        //Using (__bridge_transfer NSData *) casts the provider to type NSData and gives ownership to ARC, but still not discarded        NSData *data = (__bridge_transfer NSData *)CGDataProviderCopyData(provider);                const UInt8 *bytes = (Byte *)[data bytes];                // Populate byte array with channel data from each pixel        for(size_t row = 0; row < height; row++) {                        for(size_t col = 0; col < width; col++) {                                const UInt8* pixel = &bytes[row * bpr + col * bytes_per_pixel];                for(unsigned short i = 0; i < 4; i+=4) {                                        unsigned short red = pixel[i];                  // red channel                    unsigned short green = pixel[i+1];              // green channel                    unsigned short blue = pixel[i+2];               // blue channel                    unsigned short alpha = pixel[i+3];              // alpha channel                                        [byteArray addObject:@(red)];                    [byteArray addObject:@(green)];                    [byteArray addObject:@(blue)];                    [byteArray addObject:@(alpha)];                }            }        }        data = nil;    }    return byteArray;}

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