IOS 如何根据实际图像比例调整图像大小并给出自定义大小？

Question

Resize UIImage with custom size by checking actual image ratio for reducing image size. I have already tried this UIImageJPEGRepresentation(Image, 0.8); but problem with this is that image quality is reducing. Any help would be really appreciated. Thank you

Answer 1

Pass UIImage to below method which resize your image with custom height/width and you can also give compression value of image for reducing image size and Check image size before and after resizing.

Here is sample method-

-(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];

}

This will help you..:)

Answer 2

+ (UIImage *)resizeImage:(UIImage *)image toSize:(CGSize)newSize {
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

very easy way to do this.