1、圖片等比例壓縮

//等比例壓縮
-(UIImage *) imageCompressForSize:(UIImage *)sourceImage targetSize:(CGSize)size{
    UIImage *newImage = nil;
    CGSize imageSize = sourceImage.size;
    CGFloat width = imageSize.width;
    CGFloat height = imageSize.height;
    CGFloat targetWidth = size.width;
    CGFloat targetHeight = size.height;
    CGFloat scaleFactor = 0.0;
    CGFloat scaledWidth = targetWidth;
    CGFloat scaledHeight = targetHeight;
    CGPoint thumbnailPoint = CGPointMake(0.0, 0.0);
    if(CGSizeEqualToSize(imageSize, size) == NO){
        CGFloat widthFactor = targetWidth / width;
        CGFloat heightFactor = targetHeight / height;
        if(widthFactor > heightFactor){
            scaleFactor = widthFactor;
        }
        else{
            scaleFactor = heightFactor;
        }
        scaledWidth = width * scaleFactor;
        scaledHeight = height * scaleFactor;
        if(widthFactor > heightFactor){
            thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
        }else if(widthFactor < heightFactor){
            thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
        }
    }
    UIGraphicsBeginImageContext(size);
    CGRect thumbnailRect = CGRectZero;
    thumbnailRect.origin = thumbnailPoint;
    thumbnailRect.size.width = scaledWidth;
    thumbnailRect.size.height = scaledHeight;
    [sourceImage drawInRect:thumbnailRect];
    newImage = UIGraphicsGetImageFromCurrentImageContext();
    if(newImage == nil){
        NSLog(@"scale image fail");
    }
    UIGraphicsEndImageContext();
    return newImage;
}

2蝎困、把圖片等比例壓縮到指定寬度

//指定寬度按比例縮放
-(UIImage *) imageCompressForWidthScale:(UIImage *)sourceImage targetWidth:(CGFloat)defineWidth{
    
    UIImage *newImage = nil;
    CGSize imageSize = sourceImage.size;
    CGFloat width = imageSize.width;
    CGFloat height = imageSize.height;
    CGFloat targetWidth = defineWidth;
    CGFloat targetHeight = height / (width / targetWidth);
    CGSize size = CGSizeMake(targetWidth, targetHeight);
    CGFloat scaleFactor = 0.0;
    CGFloat scaledWidth = targetWidth;
    CGFloat scaledHeight = targetHeight;
    CGPoint thumbnailPoint = CGPointMake(0.0, 0.0);
    
    if(CGSizeEqualToSize(imageSize, size) == NO){
        
        CGFloat widthFactor = targetWidth / width;
        CGFloat heightFactor = targetHeight / height;
        
        if(widthFactor > heightFactor){
            scaleFactor = widthFactor;
        }
        else{
            scaleFactor = heightFactor;
        }
        scaledWidth = width * scaleFactor;
        scaledHeight = height * scaleFactor;
        
        if(widthFactor > heightFactor){
            
            thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
            
        }else if(widthFactor < heightFactor){
            
            thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
        }
    }
    UIGraphicsBeginImageContext(size);
    CGRect thumbnailRect = CGRectZero;
    thumbnailRect.origin = thumbnailPoint;
    thumbnailRect.size.width = scaledWidth;
    thumbnailRect.size.height = scaledHeight;
    [sourceImage drawInRect:thumbnailRect];
    newImage = UIGraphicsGetImageFromCurrentImageContext();
    if(newImage == nil){
        
        NSLog(@"scale image fail");
    }  
    UIGraphicsEndImageContext();  
    return newImage;  
}

3、截取當(dāng)前頁(yè)面生成圖片（屏幕外的也包括在內(nèi)）

func captureScorllview(scrollView:UIScrollView) -> UIImage {
        var image = UIImage()
        UIGraphicsBeginImageContext(scrollView.contentSize)
        let savedContentOffset  = scrollView.contentOffset
        let savedFrame = scrollView.frame
        scrollView.contentOffset = .zero
        scrollView.frame = CGRect(x: 0, y: 0, width: scrollView.contentSize.width, height: scrollView.contentSize.height + 100)
        scrollView.layer.render(in: UIGraphicsGetCurrentContext()!)
        image = UIGraphicsGetImageFromCurrentImageContext()!
        let context = CIContext(options: nil)
        var inputImage = CIImage(image: image)
        let options:[String : AnyObject] = [CIDetectorImageOrientation:1 as AnyObject] //圖片方向
        let filters = inputImage!.autoAdjustmentFilters(options: options)
        //遍歷所有濾鏡，依次處理圖像
        for filter: CIFilter in filters {
            filter.setValue(inputImage, forKey: kCIInputImageKey)
            inputImage = filter.outputImage
        }
        let cgImage = context.createCGImage(inputImage!, from: inputImage!.extent)
        image = UIImage(cgImage: cgImage!)
        scrollView.contentOffset = savedContentOffset
        scrollView.frame = savedFrame
        UIGraphicsEndImageContext()
        return image
    }