代码大放送--iOS图片压缩

最近需要用到图片压缩，本来苹果是有一个图片压缩的方法的，但是函数只能说不是很符合我们现在的需求，尤其是一张几M的图片想要压缩成40K用苹果的API这是不可能做到的，我在网络上查找了很多资料，都没有相关现成的第三方库或方法给我用，后来我绝望了，只能自己写一个了。
以下是我设计这个压缩图片的思路----
（1）先根据原图跟需要压缩成多少KB算出压缩的比例。
（2）获取原图的Size，根据算出的比例来计算出缩小后的图片Size
（3）再通过判断原图的宽跟高的比例，通过反推，计算出压缩后小图的宽跟高
（4）重新渲染图片，再回调出来

以下是代码部分
Swift 代码部分

// 图片回调代理
typealias ImageBlock = (image:UIImage) -> Void

/**
 压缩图片
 - parameter image:      需要压缩的图片
 - parameter imageBytes: 压缩的大小
 - parameter block:      压缩后的回调
 */
func compressedImageFiles(image:UIImage?, imageBytes:CGFloat = 30, block:ImageBlock){
    var imageCope = image
    let fBytes = imageBytes * 1024
    
    var uploadImageData:NSData?
    
    uploadImageData = UIImagePNGRepresentation(imageCope!)
    
    let imageSize = imageCope!.size
    let imageWidth = imageSize.width
    let imageHeight = imageSize.height
    
    if CGFloat((uploadImageData?.length)!) > fBytes {
        
        dispatch_async(dispatch_queue_create("CompressedImage", DISPATCH_QUEUE_SERIAL)) { () -> Void in
            
            let fBytes = fBytes/CGFloat((uploadImageData?.length)!)
            
            let fScaleArea = imageWidth * imageHeight * fBytes
            
            var fImageScale:CGFloat = 0.0
            
            var dHeight:CGFloat? = 0.0
            
            var dWidth:CGFloat? = 0.0
            
            if imageWidth > imageHeight {
                
                fImageScale = imageWidth/imageHeight
                dHeight = CGFloat(sqrt(Double(fScaleArea/fImageScale)))
                dWidth = dHeight! * fImageScale
            }
            else if imageHeight > imageWidth {
                
                fImageScale = imageHeight/imageWidth
                dWidth = CGFloat(sqrt(Double(fScaleArea/fImageScale)))
                dHeight = dWidth! * fImageScale
            }
            else
            {
                dWidth = CGFloat(sqrt(Double(fScaleArea)))
                dHeight = dWidth!
            }
            
            UIGraphicsBeginImageContext(CGSizeMake(dWidth!, dHeight!))
            imageCope!.drawInRect(CGRectMake(0, 0, dWidth!, dHeight!))
            imageCope = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()
            
            uploadImageData = UIImagePNGRepresentation(imageCope!)
            
            if CGFloat((uploadImageData?.length)!) > fBytes {
                uploadImageData = UIImageJPEGRepresentation(imageCope!, 1);
            }
            print("图片已经压缩成\(uploadImageData!.length/1024)KB")
            
            imageCope = UIImage(data: uploadImageData!)!
            
            dispatch_sync(dispatch_get_main_queue(), { () -> Void in
                block(image: imageCope!)
            })
        }
    }
    else
    {
         block(image: imageCope!)
    }
}

Swift代码调用上面函数

/**
 *  这句函数调用的意思是，将 1.jpg 这张图片压缩成 100KB 左右的大小
 */
self.compressedImageFiles(UIImage(named: "1.jpg"), imageBytes: 100) { (image) in
    print("这个是压缩后的图片\(image)")
}

下面部分是用OC代码部分
OC 代码

/**
 *  压缩图片
 *
 *  @param image       需要压缩的图片
 *  @param fImageBytes 希望压缩后的大小(以KB为单位)
 *
 *  @return 压缩后的图片
 */
- (void)compressedImageFiles:(UIImage *)image
              imageBytes:(CGFloat)fImageBytes
              imageBlock:(imageBlock)block
{
    __block UIImage *imageCope = image;
    fImageBytes = fImageBytes * 1024;

    __block NSData *uploadImageData = nil;

    uploadImageData = UIImagePNGRepresentation(imageCope);
    CGSize size = imageCope.size;
    CGFloat imageWidth = size.width;
    CGFloat imageHeight = size.height;

    if (uploadImageData.length > fImageBytes) {
    
        dispatch_async(dispatch_queue_create("CompressedImage", DISPATCH_QUEUE_SERIAL), ^{
        
            CGFloat fBytes = fImageBytes/uploadImageData.length;
        
            CGFloat fScaleArea = imageWidth * imageHeight * fBytes;
        
            CGFloat fImageScale = 0.0;
        
            CGFloat dHeight = 0.0;
        
            CGFloat dWidth = 0.0;
        
            if (imageWidth > imageHeight) {
            
                fImageScale = imageWidth/imageHeight;
                dHeight = sqrtf(fScaleArea/fImageScale);
                dWidth  = dHeight * fImageScale;
            }
            else if (imageHeight > imageWidth) {
            
                fImageScale = imageHeight/imageWidth;
                dWidth = sqrtf(fScaleArea/fImageScale);
                dHeight  = dWidth * fImageScale;
            }
            else {
            
                dWidth = sqrtf(fScaleArea);
                dHeight = dWidth;
            }
        
            UIGraphicsBeginImageContext(CGSizeMake(dWidth, dHeight));
            [imageCope drawInRect:CGRectMake(0, 0, dWidth, dHeight)];
            imageCope = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
        
            uploadImageData = UIImagePNGRepresentation(imageCope);
        
            if (uploadImageData.length > fImageBytes) {
                uploadImageData = UIImageJPEGRepresentation(imageCope, 1);
            }
            NSLog(@"图片已经压缩成 %luKB",uploadImageData.length/1024);
            imageCope = [[UIImage alloc] initWithData:uploadImageData];
        
            dispatch_sync(dispatch_get_main_queue(), ^{
                block(imageCope);
            });
        });
    }
    else
    {
        block(imageCope);
    }
}

OC调用代码

/**
 *  这句函数调用的意思是，将 1.jpg 这张图片压缩成 100KB 左右的大小
 */
[self compressedImageFiles:[UIImage imageNamed:@"1.jpg"] imageBytes:100 imageBlock:^(UIImage *image) {
    
    NSLog(@"这个是压缩后的图片%@",image);
}];

希望大家不吝赐教。。。
代码已经修改，删除不人性化的地方~！
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