手機中經(jīng)常會遇到一些非常大的圖片,當把它們導(dǎo)入到我們的緩存時有時會造成程序的閃退,即超過了125mb,此時我們有三種方法對圖片進行壓縮,前兩者方法http://blog.csdn.NET/mideveloper/article/details/11473627這位哥們講的已經(jīng)很詳細了,我自己用OC和Swift寫了一個UIImage的分類,也比較好用.

OC:

+(UIImage *)reduceScaleToWidth:(CGFloat)width andImage:(UIImage *)image{
        
        if (image.size.width <= width) {
            return image;
        }
        
        CGFloat height = image.size.height * (width/image.size.width);
        
        CGRect rect = CGRectMake(0, 0, width, height);
        
        UIGraphicsBeginImageContext(rect.size);
        
        [image drawInRect:rect];
        
        UIImage * returnImage = UIGraphicsGetImageFromCurrentImageContext();
        
        UIGraphicsEndImageContext();
        
        return returnImage;
    }

SWIFT

    /// 將圖片按指定寬度縮放
    ///
    /// - parameter width: 指定寬度
    ///
    /// - returns: <#return value description#>
    func scaleToWidth(width: CGFloat) -> UIImage {
        if size.width <= width {
            return self
        }
        
        // 計算高度
        let height = size.height * (width / size.width)
        let rect = CGRect(x: 0, y: 0, width: width, height: height)
        
        // 開啟圖形上下文
        UIGraphicsBeginImageContext(rect.size)
        
        // 畫
        self.drawInRect(rect)
        
        // 取
        let image = UIGraphicsGetImageFromCurrentImageContext()
        
        // 關(guān)閉上下文
        UIGraphicsEndImageContext()
        
        return image
    }