Using C# how can I resize a jpeg image?

Question

Using C# how can I resize a jpeg image? A code sample would be great.

Answer 1

Nice example.

public static Image ResizeImage(Image sourceImage, int maxWidth, int maxHeight)
{
    // Determine which ratio is greater, the width or height, and use
    // this to calculate the new width and height. Effectually constrains
    // the proportions of the resized image to the proportions of the original.
    double xRatio = (double)sourceImage.Width / maxWidth;
    double yRatio = (double)sourceImage.Height / maxHeight;
    double ratioToResizeImage = Math.Max(xRatio, yRatio);
    int newWidth = (int)Math.Floor(sourceImage.Width / ratioToResizeImage);
    int newHeight = (int)Math.Floor(sourceImage.Height / ratioToResizeImage);

    // Create new image canvas -- use maxWidth and maxHeight in this function call if you wish
    // to set the exact dimensions of the output image.
    Bitmap newImage = new Bitmap(newWidth, newHeight, PixelFormat.Format32bppArgb);

    // Render the new image, using a graphic object
    using (Graphics newGraphic = Graphics.FromImage(newImage))
    {
        using (var wrapMode = new ImageAttributes())
        {
            wrapMode.SetWrapMode(WrapMode.TileFlipXY);
            newGraphic.DrawImage(image, destRect, 0, 0, image.Width, image.Height, GraphicsUnit.Pixel, wrapMode);
        }

        // Set the background color to be transparent (can change this to any color)
        newGraphic.Clear(Color.Transparent);

        // Set the method of scaling to use -- HighQualityBicubic is said to have the best quality
        newGraphic.InterpolationMode = InterpolationMode.HighQualityBicubic;

        // Apply the transformation onto the new graphic
        Rectangle sourceDimensions = new Rectangle(0, 0, sourceImage.Width, sourceImage.Height);
        Rectangle destinationDimensions = new Rectangle(0, 0, newWidth, newHeight);
        newGraphic.DrawImage(sourceImage, destinationDimensions, sourceDimensions, GraphicsUnit.Pixel);
    }

    // Image has been modified by all the references to it's related graphic above. Return changes.
    return newImage;
}

Source : http://mattmeisinger.com/resize-image-c-sharp