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);
}];