UIImage图片处理（更改颜色，修改透明度，缩小，合并图片）

//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<<span
class="s5">200 && image.size.height<<span class="s5">200)

    {

        return image;

    }

    UIGraphicsBeginImageContext(size);

    CGRect rect = CGRectMake(0, 0,
size.width, size.height);

    [image drawInRect:rect];

    UIImage *newing = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return newing;

}