圖片剪裁iOS代碼

實現按照某一長寬比例，剪裁圖片的上部和下部，保留中間的內容。當然也可以自定義需要剪裁留下的區域。在使用前需要添加Framework：CoreGraphics.framework。

代碼：

    - (UIImage*) crop:(UIImage*)theImage{  
        // Get size of current image  
        CGSize size = [theImage size];  

        // Create rectangle that represents a cropped image  
        CGFloat desiredRatio = 1.2;  

        CGFloat croppedWidth = 0.0;  
        CGFloat croppedHeight = 0.0;  

        CGRect rect;  

        if (size.height/size.width >= desiredRatio) {  
            croppedWidth = size.width;  
            croppedHeight = size.width * desiredRatio;  
            CGFloat difference = (size.height-croppedHeight)/2;  
            rect = CGRectMake(0.0, difference ,croppedWidth, croppedHeight);  
        }  
        else{  
            return theImage;  
        }  

        // Create bitmap image from original image data,  
        // using rectangle to specify desired crop area  
        CGImageRef imageRef = CGImageCreateWithImageInRect([theImage CGImage], rect);  
        UIImage *croppedImage = [UIImage imageWithCGImage:imageRef];  
        CGImageRelease(imageRef);  
        return croppedImage;  
    }