How to proportional resize image of any type in .NET?

问题

Is possible to resize image proportionally in a way independent of the image type (bmp, jpg, png, etc)?

I have this code and know that something is missing (but don't know what):

public bool ResizeImage(string fileName, string imgFileName,
    ImageFormat format, int width, int height)
{
    try
    {
        using (Image img = Image.FromFile(fileName))
        {
            Image thumbNail = new Bitmap(width, height, img.PixelFormat);
            Graphics g = Graphics.FromImage(thumbNail);
            g.CompositingQuality = CompositingQuality.HighQuality;
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            Rectangle rect = new Rectangle(0, 0, width, height);
            g.DrawImage(img, rect);
            thumbNail.Save(imgFileName, format);
        }
        return true;
    }
    catch (Exception)
    {
        return false;
    }
}

If not possible, how can I resize proportional a jpeg image?

I know that using this method, but don't know where to put this (!).

回答1:

First and foremost, you're not grabbing the CURRENT height and width of the image. In order to resize proportionately you'll need to grab the current height/width of the image and resize based on that.

From there, find the greatest attribute and resize proportionately based on that.

For instance, let's say the current image is 800 x 600 and you wanna resize proportionately within a 400 x 400 space. Grab the greatest proportion (800) and find it's ratio to the new size. 800 -> 400 = .5 Now take that ratio and multiply by the second dimension (600 * .5 = 300).

Your new size is 400 x 300. Here's a PHP example (sorry....you'll get it though)

$thumb_width = 400;
$thumb_height = 400;

$orig_w=imagesx($src_img); 
$orig_h=imagesy($src_img);      

if ($orig_w>$orig_h){//find the greater proportion
    $ratio=$thumb_width/$orig_w; 
    $thumb_height=$orig_h*$ratio;
}else{
    $ratio=$thumb_height/$orig_h; 
    $thumb_width=$orig_w*$ratio;
}

回答2:

I think your code is fine, but taking in the width and the height as parameters is where you're going wrong in my opinion. Why should the caller of this method have to decide how big they want the width and the height? I would suggest changing it to a percentage:

public bool ResizeImage(string fileName, string imgFileName,
    ImageFormat format, int percent)
{
    try
    {
        using (Image img = Image.FromFile(fileName))
        {
            int width = img.Width * (percent * .01);
            int height = img.Height * (percent * .01);
            Image thumbNail = new Bitmap(width, height, img.PixelFormat);
            Graphics g = Graphics.FromImage(thumbNail);
            g.CompositingQuality = CompositingQuality.HighQuality;
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            Rectangle rect = new Rectangle(0, 0, width, height);
            g.DrawImage(img, rect);
            thumbNail.Save(imgFileName, format);
        }
        return true;
    }
    catch (Exception)
    {
        return false;
    }
}

来源：https://stackoverflow.com/questions/703873/how-to-proportional-resize-image-of-any-type-in-net

标签

.net

graphics

image-manipulation