图片添加杂色噪点

/**
 *  伪随机数
 */
static NSInteger ATNoiseRseed = 115;
static inline NSInteger ATNoiseRand() {
    return (ATNoiseRseed = (ATNoiseRseed * 214013 + 2531011) & ((1U << 31) - 1)) >> 16;
}
/**
 *  图片加入杂色, intensity: 0.0 ~ 1.0f, gary: YES标示单色噪点
 */
- (UIImage *)imageWithNoiseIntensity:(CGFloat)intensity gray:(BOOL)isGray
{
    UIImage *image;
    int width = self.size.width * self.scale;
    int height = self.size.height * self.scale;

    CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
    if (colorspace == NULL) {
        ATLog(@"Create Colorspace Error!");
        return nil;
    }

    Byte *imgData = NULL;
    imgData = malloc(width * height * 4);
    if (imgData == NULL) {
        ATLog(@"Memory Error!");
        CGColorSpaceRelease(colorspace);
        return nil;
    }

    CGContextRef bmpContext = CGBitmapContextCreate(imgData, width, height, 8, width * 4, colorspace, (CGBitmapInfo)kCGImageAlphaPremultipliedLast);
    if (!bmpContext) {
        ATLog(@"Create Bitmap context Error!");
        CGColorSpaceRelease(colorspace);
        return nil;
    }

    CGContextDrawImage(bmpContext, CGRectMake(0, 0, width, height), self.CGImage);
    for (long i = 0; i < width * height; i++) {
        int randR = (ATNoiseRand()%511-255) * intensity;
        int randG = isGray ? randR : (ATNoiseRand()%511-255) * intensity;
        int randB = isGray ? randR : (ATNoiseRand()%511-255) * intensity;

        imgData[4*i+0] = MAX(0, MIN(255, (imgData[4*i+0] + randR)));
        imgData[4*i+1] = MAX(0, MIN(255, (imgData[4*i+1] + randG)));
        imgData[4*i+2] = MAX(0, MIN(255, (imgData[4*i+2] + randB)));
        imgData[4*i+3] = 255;
    }

    CGImageRef imageRef = CGBitmapContextCreateImage(bmpContext);
    if (imageRef != NULL) {
        image = [[UIImage alloc] initWithCGImage:imageRef];
        CGImageRelease(imageRef);
    }

    CGColorSpaceRelease(colorspace);
    CGContextRelease(bmpContext);
    free(imgData);

    return image;
}

为UIImage添加分类，图片加入杂色, intensity: 0.0 ~ 1.0f, gary: YES标示单色噪点。