C# – Resize image proportionally with MaxHeight and MaxWidth constraints

cgdi+image processingnetwinforms

Using System.Drawing.Image.

If an image width or height exceed the maximum, it need to be resized proportionally .
After resized it need to make sure that neither width or height still exceed the limit.

The Width and Height will be resized until it is not exceed to maximum and minimum automatically (biggest size possible) and also maintain the ratio.

Best Answer

Like this?

public static void Test()
{
    using (var image = Image.FromFile(@"c:\logo.png"))
    using (var newImage = ScaleImage(image, 300, 400))
    {
        newImage.Save(@"c:\test.png", ImageFormat.Png);
    }
}

public static Image ScaleImage(Image image, int maxWidth, int maxHeight)
{
    var ratioX = (double)maxWidth / image.Width;
    var ratioY = (double)maxHeight / image.Height;
    var ratio = Math.Min(ratioX, ratioY);

    var newWidth = (int)(image.Width * ratio);
    var newHeight = (int)(image.Height * ratio);

    var newImage = new Bitmap(newWidth, newHeight);

    using (var graphics = Graphics.FromImage(newImage))
        graphics.DrawImage(image, 0, 0, newWidth, newHeight);

    return newImage;
}
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