iOS如何根据实际图像比例调整图像大小并指定自定义大小？

user6274686 发表于 Dev

用户名

调整大小UIImage与custom size通过检查实际的图像比用于降低图像的大小。我已经尝试过了，UIImageJPEGRepresentation(Image, 0.8);但是问题是图像质量下降了。任何帮助将非常感激。谢谢

罗希特·坎德尔瓦尔（Rohit Khandelwal）

传递UIImage到下面的方法，该方法可以使用自定义的高度/宽度来调整图像的大小，还可以提供图像的压缩值以减小图像大小，并在调整大小之前和之后检查图像大小。

这是示例方法-

-(UIImage *)resizeImage:(UIImage *)image
{

    NSInteger imageActualSize = UIImageJPEGRepresentation(image,1).length;

    NSLog(@"size of IMAGE before resizing: %@ ", [NSByteCountFormatter stringFromByteCount:imageActualSize countStyle:NSByteCountFormatterCountStyleFile]);

    float actualHeight = image.size.height;
    float actualWidth = image.size.width;
    float maxHeight = 400.0; // your custom  height
    float maxWidth = 350; // your custom  width
    float imgRatio = actualWidth/actualHeight;
    float maxRatio = maxWidth/maxHeight;
    float compressionQuality = 0.5;//50 percent compression

    if (actualHeight > maxHeight || actualWidth > maxWidth)
    {
        if(imgRatio < maxRatio)
        {
            //adjust width according to maxHeight
            imgRatio = maxHeight / actualHeight;
            actualWidth = imgRatio * actualWidth;
            actualHeight = maxHeight;
        }
        else if(imgRatio > maxRatio)
        {
            //adjust height according to maxWidth
            imgRatio = maxWidth / actualWidth;
            actualHeight = imgRatio * actualHeight;
            actualWidth = maxWidth;
        }
        else
        {
            actualHeight = maxHeight;
            actualWidth = maxWidth;
        }
    }

    CGRect rect = CGRectMake(0.0, 0.0, actualWidth, actualHeight);
    UIGraphicsBeginImageContext(rect.size);
    [image drawInRect:rect];
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    NSData *imageData = UIImageJPEGRepresentation(img, compressionQuality);
    UIGraphicsEndImageContext();

    NSInteger imageReduceSize = imageData.length;

    NSLog(@"size of IMAGE after resizing: %@ ",[NSByteCountFormatter stringFromByteCount:imageReduceSize countStyle:NSByteCountFormatterCountStyleFile]);

    return [UIImage imageWithData:imageData];

}