ios UIImage转RGB

有时由于一些特殊目的, 需要一些RGB数据

+ (unsigned char *)rgbArray: (UIImage *) uiimage
{
    CGImageRef image = [uiimage CGImage];
    CGSize size = uiimage.size;
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    int pixelCount = size.width * size.height;
    uint8_t* rgba = malloc(pixelCount * 4);
    CGContextRef context = CGBitmapContextCreate(rgba, size.width, size.height, 8, 4 * size.width, colorSpace, kCGImageAlphaPremultipliedLast);
    CGContextDrawImage(context, CGRectMake(0, 0, size.width, size.height), image);
    CGContextRelease(context);
    uint8_t* rgb = malloc(pixelCount * 3);
    int m = 0;
    int n = 0;
    /** 移除掉Alpha */
    for(int i=0; i<pixelCount; i++){
        rgb[m++] = rgba[n++];
        rgb[m++] = rgba[n++];
        rgb[m++] = rgba[n++];
        n++;
    }
    free(rgba);
    return rgb;
}