(转)UIImage图片处理(更改颜色,修改透明度,缩小,合并图片)

转自:http://blog.sina.com.cn/s/blog_64cfe8f00101pm3x.html
//遍历图片像素,更改图片颜色
void ProviderReleaseData (void *info, const void data, size_t size)
{
free((void
)data);
}

  • (UIImage) imageBlackToTransparent:(UIImage) image
    {
    // 分配内存
    const int imageWidth = image.size.width;
    const int imageHeight = image.size.height;
    size_t bytesPerRow = imageWidth * 4;
    uint32_t* rgbImageBuf = (uint32_t*)malloc(bytesPerRow * imageHeight);

    // 创建context
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(rgbImageBuf, imageWidth, imageHeight, 8, bytesPerRow, colorSpace,
    kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
    CGContextDrawImage(context, CGRectMake(0, 0, imageWidth, imageHeight), image.CGImage);

    // 遍历像素
    int pixelNum = imageWidth * imageHeight;
    uint32_t* pCurPtr = rgbImageBuf;
    for (int i = 0; i < pixelNum; i++, pCurPtr++)
    {
    if ((pCurPtr & 0xFFFFFF00) == 0xffffff00) // 将白色变成透明
    {
    uint8_t
    ptr = (uint8_t)pCurPtr;
    ptr[0] = 0;
    }
    else
    {
    // 改成下面的代码,会将图片转成想要的颜色
    uint8_t
    ptr = (uint8_t*)pCurPtr;
    ptr[3] = 0; //0~255
    ptr[2] = 0;
    ptr[1] = 0;

      }
    

    }

    // 将内存转成image
    CGDataProviderRef dataProvider = CGDataProviderCreateWithData(NULL, rgbImageBuf, bytesPerRow * imageHeight, ProviderReleaseData);
    CGImageRef imageRef = CGImageCreate(imageWidth, imageHeight, 8, 32, bytesPerRow, colorSpace,
    kCGImageAlphaLast | kCGBitmapByteOrder32Little, dataProvider,
    NULL, true, kCGRenderingIntentDefault);
    CGDataProviderRelease(dataProvider);

    UIImage* resultUIImage = [UIImage imageWithCGImage:imageRef];

    // 释放
    CGImageRelease(imageRef);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    // free(rgbImageBuf) 创建dataProvider时已提供释放函数,这里不用free

    return resultUIImage;
    }

//设置图片透明度

  • (UIImage )imageByApplyingAlpha:(CGFloat)alpha image:(UIImage)image
    {
    UIGraphicsBeginImageContextWithOptions(image.size, NO, 0.0f);

    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGRect area = CGRectMake(0, 0, image.size.width, image.size.height);

    CGContextScaleCTM(ctx, 1, -1);
    CGContextTranslateCTM(ctx, 0, -area.size.height);

    CGContextSetBlendMode(ctx, kCGBlendModeMultiply);

    CGContextSetAlpha(ctx, alpha);

    CGContextDrawImage(ctx, area, image.CGImage);

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return newImage;
    }

//合并2张图片

  • (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2 {
    UIGraphicsBeginImageContext(image2.size);

    // Draw image1
    [image1 drawInRect:CGRectMake(0, 0, image1.size.width, image1.size.height)];

    // Draw image2
    [image2 drawInRect:CGRectMake(0, 0, image2.size.width, image2.size.height)];

    UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return resultingImage;
    }

//将UIImage缩放到指定大小尺寸:

  • (UIImage *)scaleToSize:(UIImage )img size:(CGSize)size{
    // 创建一个bitmap的context
    // 并把它设置成为当前正在使用的context
    UIGraphicsBeginImageContext(size);
    // 绘制改变大小的图片
    [img drawInRect:CGRectMake(0, 0, size.width, size.height)];
    // 从当前context中创建一个改变大小后的图片
    UIImage
    scaledImage = UIGraphicsGetImageFromCurrentImageContext();
    // 使当前的context出堆栈
    UIGraphicsEndImageContext();
    // 返回新的改变大小后的图片
    return scaledImage;
    }

//根据图片的大小等比例压缩返回图片
-(UIImage *)fitSmallImage:(UIImage *)image size:(CGSize)size
{
if (nil == image)
{
return nil;
}
if (image.size.width<200 && image.size.height<200)
{
return image;
}
UIGraphicsBeginImageContext(size);
CGRect rect = CGRectMake(0, 0, size.width, size.height);
[image drawInRect:rect];
UIImage *newing = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newing;
}

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