iOS图片马赛克处理

1、马赛克算法原理
把某一点的色值填充周围的区域，这样看起来会有原图的轮廓，又不会完全看不清
2、算法实现,参考：http://www.cnblogs.com/vicstudio/p/3358358.html

+(UIImage *)mosaicImage:(UIImage *)sourceImage mosaicLevel:(NSUInteger)level{
    
    //1、这一部分是为了把原始图片转成位图，位图再转成可操作的数据
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();//颜色通道
    CGImageRef imageRef = sourceImage.CGImage;//位图
    CGFloat width = CGImageGetWidth(imageRef);//位图宽
    CGFloat height = CGImageGetHeight(imageRef);//位图高
    CGContextRef context = CGBitmapContextCreate(nil, width, height, 8, width * 4, colorSpace, kCGImageAlphaPremultipliedLast);//生成上下文
    CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, width, height), imageRef);//绘制图片到上下文中
    unsigned char *bitmapData = CGBitmapContextGetData(context);//获取位图的数据
    
    
    //2、这一部分是往右往下填充色值
    NSUInteger index,preIndex;
    unsigned char pixel[4] = {0};
    for (int i = 0; i < height; i++) {//表示高，也可以说是行
        for (int j = 0; j < width; j++) {//表示宽，也可以说是列
            index = i * width + j;
            if (i % level == 0) {
                if (j % level == 0) {
                    //把当前的色值数据保存一份，开始为i=0，j=0，所以一开始会保留一份
                    memcpy(pixel, bitmapData + index * 4, 4);
                }else{
                    //把上一次保留的色值数据填充到当前的内存区域，这样就起到把前面数据往后挪的作用，也是往右填充
                    memcpy(bitmapData +index * 4, pixel, 4);
                }
            }else{
                //这里是把上一行的往下填充
                preIndex = (i - 1) * width + j;
                memcpy(bitmapData + index * 4, bitmapData + preIndex * 4, 4);
            }
        }
    }
    
    //把数据转回位图，再从位图转回UIImage
    NSUInteger dataLength = width * height * 4;
    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, bitmapData, dataLength, NULL);
    CGImageRef mosaicImageRef = CGImageCreate(width, height,
                                              8,
                                              32,
                                              width*4 ,
                                              colorSpace,
                                              kCGBitmapByteOrderDefault,
                                              provider,
                                              NULL, NO,
                                              kCGRenderingIntentDefault);
    CGContextRef outputContext = CGBitmapContextCreate(nil,
                                                       width,
                                                       height,
                                                       8,
                                                       width*4,
                                                       colorSpace,
                                                       kCGImageAlphaPremultipliedLast);
    CGContextDrawImage(outputContext, CGRectMake(0.0f, 0.0f, width, height), mosaicImageRef);
    CGImageRef resultImageRef = CGBitmapContextCreateImage(outputContext);
    UIImage *resultImage = nil;
    if([UIImage respondsToSelector:@selector(imageWithCGImage:scale:orientation:)]) {
        float scale = [[UIScreen mainScreen] scale];
        resultImage = [UIImage imageWithCGImage:resultImageRef scale:scale orientation:UIImageOrientationUp];
    } else {
        resultImage = [UIImage imageWithCGImage:resultImageRef];
    }
    CFRelease(resultImageRef);
    CFRelease(mosaicImageRef);
    CFRelease(colorSpace);
    CFRelease(provider);
    CFRelease(context);
    CFRelease(outputContext);
    return resultImage;
}

- (void)initView{
    UIImage *img = [UIImage imageNamed:@"cat.jpg"];
    UIImage *newImg = [[self class] mosaicImage:img mosaicLevel:20];
}

原图.png
效果图.png

3、demo地址：https://github.com/lihxCode/mosaicImage/tree/master