iOS 图片处理方法（按比例缩放,指定宽度按比例缩放)

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今天遇见的处理图片的问题，一张图片上下两个部分都有一个空白区域，就中间是图片。要求是不能让他显示上下    有空白问间距。这是测试提出来的问题，但是图片本身就是这个毛病。无奈，哥哥改。谁有好的方法推荐推荐推荐      啊!!!

   两个方法如下

   建议让这两个放在UIImage的延展里，方便以后使用。

    1：按比例缩放

    在这里你传入的cgsize就是你要放大的区域，或者就是说设置放大的区域部分

     

//按比例缩放,size 是你要把图显示到 多大区域 
+ (UIImage *) imageCompressFitSizeScale:(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：按比例缩放

 这个代码很有意思

//指定宽度按比例缩放
-(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;
}

 

调用

UIImage *headImage = [UIImage imageWithContentsOfFile:imagePath];

        

        UIImage * newHeadImage = [UIImage imageCompressForSize:headImage targetSize:CGSizeMake(200, 140)];

        

        if (newHeadImage==nil) {

            newHeadImage = [UIImage imageNamed:@"headIcon"];

        }

        self.headerImageView.image = newHeadImage;