iOS应用中图片尺寸的处理

在项目中有时会对图片的尺寸进行处理，大小的设定，裁剪等要求，下面是一些我在项目中用到的代码：

1.

//修改图片的尺寸

- (UIImage *)reSizeImage:(UIImage *)image toSize:(CGSize)reSize{

    

    UIGraphicsBeginImageContext(CGSizeMake(reSize.width, reSize.height));

    [image drawInRect:CGRectMake(0,0, reSize.width, reSize.height)];

    

    UIImage *reSizeImage =UIGraphicsGetImageFromCurrentImageContext();

    

    UIGraphicsEndImageContext();

    

    return reSizeImage;

}

2.

//根据尺寸裁剪图片

- (UIImage *)handleImage:(UIImage *)originalImage withSize:(CGSize)size

{

    CGSize originalsize = [originalImagesize];

    NSLog(@"改变前图片的宽度为%f,图片的高度为%f",originalsize.width,originalsize.height);

    

    //原图长宽均小于标准长宽的，不作处理返回原图

    if (originalsize.width<size.width && originalsize.height<size.height)

    {

        return originalImage;

    }

    

    //    原图长宽均大于标准长宽的，按比例缩小至最大适应值

    elseif(originalsize.width>size.width && originalsize.height>size.height)

    {

        CGFloat rate =1.0;

        CGFloat widthRate = originalsize.width/size.width;

        CGFloat heightRate = originalsize.height/size.height;

        

        rate = widthRate>heightRate?heightRate:widthRate;

        

        CGImageRef imageRef =nil;

        

        if (heightRate>widthRate)

        {

            //originalsize.height/2-size.height*rate/2

            imageRef = CGImageCreateWithImageInRect([originalImageCGImage], CGRectMake(0,0, originalsize.width, size.height*rate));//获取图片整体部分

        }

        else

        {

            //originalsize.width/2-size.width*rate/2

            imageRef = CGImageCreateWithImageInRect([originalImageCGImage], CGRectMake(0,0, size.width*rate, originalsize.height));//获取图片整体部分

        }

        UIGraphicsBeginImageContext(size);//指定要绘画图片的大小

        CGContextRef con =UIGraphicsGetCurrentContext();

        

        CGContextTranslateCTM(con,0.0, size.height);

        CGContextScaleCTM(con,1.0, -1.0);

        

        CGContextDrawImage(con,CGRectMake(0,0, size.width, size.height), imageRef);

        

        UIImage *standardImage =UIGraphicsGetImageFromCurrentImageContext();

        NSLog(@"改变后图片的宽度为%f,图片的高度为%f",[standardImagesize].width,[standardImagesize].height);

        

        UIGraphicsEndImageContext();

        CGImageRelease(imageRef);

        

        return standardImage;

    }

    

    //原图长宽有一项大于标准长宽的，对大于标准的那一项进行裁剪，另一项保持不变

    elseif(originalsize.height>size.height || originalsize.width>size.width)

    {

        CGImageRef imageRef =nil;

        

        if(originalsize.height>size.height)

        {

            //originalsize.height/2-size.height/2

            imageRef = CGImageCreateWithImageInRect([originalImageCGImage], CGRectMake(0,0, originalsize.width, size.height));//获取图片整体部分

        }

        elseif (originalsize.width>size.width)

        {

            //originalsize.width/2-size.width/2

            imageRef = CGImageCreateWithImageInRect([originalImageCGImage], CGRectMake(0,0, size.width, originalsize.height));//获取图片整体部分

        }

        

        UIGraphicsBeginImageContext(size);//指定要绘画图片的大小

        CGContextRef con =UIGraphicsGetCurrentContext();

        

        CGContextTranslateCTM(con,0.0, size.height);

        CGContextScaleCTM(con,1.0, -1.0);

        

        CGContextDrawImage(con,CGRectMake(0,0, size.width, size.height), imageRef);

        

        UIImage *standardImage =UIGraphicsGetImageFromCurrentImageContext();

        NSLog(@"改变后图片的宽度为%f,图片的高度为%f",[standardImagesize].width,[standardImagesize].height);

        

        UIGraphicsEndImageContext();

        CGImageRelease(imageRef);

        

        return standardImage;

    }

    

    //原图为标准长宽的，不做处理

    else

    {

        return originalImage;

    }

}

裁剪的起点可以自己设置，上面是从（0，0）开始裁剪的，可以根据自己的需求改进！