What is the best way to resize an image in C#?

Problem

System’s Get() properties are Size, Width, and Height. Drawing. How can I resize an Image object in C# at runtime?

Right now, all I’m doing is making a fresh image with:

// objImage is the original Image
Bitmap objBitmap = new Bitmap(objImage, new Size(227, 171));

Asked by inutan

Solution #1

This will resize the image in good quality:

/// <summary>
/// Resize the image to the specified width and height.
/// </summary>
/// <param name="image">The image to resize.</param>
/// <param name="width">The width to resize to.</param>
/// <param name="height">The height to resize to.</param>
/// <returns>The resized image.</returns>
public static Bitmap ResizeImage(Image image, int width, int height)
{
    var destRect = new Rectangle(0, 0, width, height);
    var destImage = new Bitmap(width, height);

    destImage.SetResolution(image.HorizontalResolution, image.VerticalResolution);

    using (var graphics = Graphics.FromImage(destImage))
    {
        graphics.CompositingMode = CompositingMode.SourceCopy;
        graphics.CompositingQuality = CompositingQuality.HighQuality;
        graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
        graphics.SmoothingMode = SmoothingMode.HighQuality;
        graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;

        using (var wrapMode = new ImageAttributes())
        {
            wrapMode.SetWrapMode(WrapMode.TileFlipXY);
            graphics.DrawImage(image, destRect, 0, 0, image.Width,image.Height, GraphicsUnit.Pixel, wrapMode);
        }
    }

    return destImage;
}

Maintaining aspect ratio is left to the reader’s discretion (in fact, I don’t believe it is this function’s responsibility to do so).

In addition, this article describes some of the problems associated with image resizing. The above function will take care of the most of them, but you must still remember to save.

Answered by mpen

Solution #2

I’m not sure what the big deal is here; just keep doing what you were doing, using the overloaded Bitmap constructor to resize a picture; the only thing you were missing was a cast back to the Image data type:

public static Image resizeImage(Image imgToResize, Size size)
{
    return (Image)(new Bitmap(imgToResize, size));
}

yourImage = resizeImage(yourImage, new Size(50,50));

Answered by Matt

Solution #3

You’ll find some responses to this question, including mine:

public Image resizeImage(int newWidth, int newHeight, string stPhotoPath)
 {
     Image imgPhoto = Image.FromFile(stPhotoPath); 

     int sourceWidth = imgPhoto.Width;
     int sourceHeight = imgPhoto.Height;

     //Consider vertical pics
    if (sourceWidth < sourceHeight)
    {
        int buff = newWidth;

        newWidth = newHeight;
        newHeight = buff;
    }

    int sourceX = 0, sourceY = 0, destX = 0, destY = 0;
    float nPercent = 0, nPercentW = 0, nPercentH = 0;

    nPercentW = ((float)newWidth / (float)sourceWidth);
    nPercentH = ((float)newHeight / (float)sourceHeight);
    if (nPercentH < nPercentW)
    {
        nPercent = nPercentH;
        destX = System.Convert.ToInt16((newWidth -
                  (sourceWidth * nPercent)) / 2);
    }
    else
    {
        nPercent = nPercentW;
        destY = System.Convert.ToInt16((newHeight -
                  (sourceHeight * nPercent)) / 2);
    }

    int destWidth = (int)(sourceWidth * nPercent);
    int destHeight = (int)(sourceHeight * nPercent);


    Bitmap bmPhoto = new Bitmap(newWidth, newHeight,
                  PixelFormat.Format24bppRgb);

    bmPhoto.SetResolution(imgPhoto.HorizontalResolution,
                 imgPhoto.VerticalResolution);

    Graphics grPhoto = Graphics.FromImage(bmPhoto);
    grPhoto.Clear(Color.Black);
    grPhoto.InterpolationMode =
        System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

    grPhoto.DrawImage(imgPhoto,
        new Rectangle(destX, destY, destWidth, destHeight),
        new Rectangle(sourceX, sourceY, sourceWidth, sourceHeight),
        GraphicsUnit.Pixel);

    grPhoto.Dispose();
    imgPhoto.Dispose();
    return bmPhoto;
}

Answered by Vinzz

Solution #4

Why don’t you make use of the system? Is it possible to use the Drawing.Image.GetThumbnailImage method?

public Image GetThumbnailImage(
    int thumbWidth, 
    int thumbHeight, 
    Image.GetThumbnailImageAbort callback, 
    IntPtr callbackData)

Example:

Image originalImage = System.Drawing.Image.FromStream(inputStream, true, true);
Image resizedImage = originalImage.GetThumbnailImage(newWidth, (newWidth * originalImage.Height) / originalWidth, null, IntPtr.Zero);
resizedImage.Save(imagePath, ImageFormat.Png);

Source: http://msdn.microsoft.com/en-us/library/system.drawing.image.getthumbnailimage.aspx

Answered by Lino Silva

Solution #5

Try net-vips, which is a C# binding for libvips. Because it’s a lazy, streaming, demand-driven image processing library, it can perform actions like this without requiring the entire image to be loaded.

It includes a useful image thumbnailer, for example:

using Image image = Image.Thumbnail("image.jpg", 300, 300);
image.WriteToFile("my-thumbnail.jpg");

It also features smart crop, which allows you to intelligently choose the most significant section of an image and maintain it in focus while cropping it. Consider the following scenario:

using Image image = Image.Thumbnail("owl.jpg", 128, crop: Enums.Interesting.Attention);
image.WriteToFile("tn_owl.jpg");

Where owl.jpg is a composition that is off-center:

Gives this result:

First it shrinks the image to get the vertical axis to 128 pixels, then crops down to 128 pixels across using the attention strategy. This one looks for features in the image that might capture the eye of a person; see Smartcrop() for more information.

Answered by kleisauke

Post is based on https://stackoverflow.com/questions/1922040/how-to-resize-an-image-c-sharp