High Quality Image Scaling C#

Question

I want to scale an image in C# with quality level as good as Photoshop does. Is there any C# image processing library available to do this thing?

Answer 1

When you draw the image using GDI+ it scales quite well in my opinion. You can use this to create a scaled image.

If you want to scale your image with GDI+ you can do something like this:

Bitmap original = ...
Bitmap scaled = new Bitmap(new Size(original.Width * 4, original.Height * 4));
using (Graphics graphics = Graphics.FromImage(scaled)) {
  graphics.DrawImage(original, new Rectangle(0, 0, scaled.Width, scaled.Height));
}

Answer 2

Tested libraries like Imagemagick and GD are available for .NET

You could also read up on things like bicubic interpolation and write your own.

Answer 3

Try the different values for Graphics.InterpolationMode. There are several typical scaling algorithms available in GDI+. If one of these is sufficient for your need, you can go this route instead of relying on an external library.

Answer 4

There's an article on Code Project about using GDI+ for .NET to do photo resizing using, say, Bicubic interpolation.

There was also another article about this topic on another blog (MS employee, I think), but I can't find the link anywhere. :( Perhaps someone else can find it?

Answer 5

CodeProject articles discussing and sharing source code for scaling images:

• Two Pass Scaling using Filters
• Matrix Transformation of Images in C#, using .NET GDI+
• Resizing a Photographic image with GDI+ for .NET
• Fast Dyadic Image Scaling with Haar Transform

Answer 6

You can try dotImage, one of my company's products, which includes an object for resampling images that has 18 filter types for various levels of quality.

Typical usage is:

// BiCubic is one technique available in PhotoShop
ResampleCommand resampler = new ResampleCommand(newSize, ResampleMethod.BiCubic);
AtalaImage newImage = resampler.Apply(oldImage).Image;

in addition, dotImage includes 140 some odd image processing commands including many filters similar to those in PhotoShop, if that's what you're looking for.

Answer 7

Here's a nicely commented Image Manipulation helper class that you can look at and use. I wrote it as an example of how to perform certain image manipulation tasks in C#. You'll be interested in the ResizeImage function that takes a System.Drawing.Image, the width and the height as the arguments.

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;

namespace DoctaJonez.Drawing.Imaging
{
    /// <summary>
    /// Provides various image untilities, such as high quality resizing and the ability to save a JPEG.
    /// </summary>
    public static class ImageUtilities
    {    
        /// <summary>
        /// A quick lookup for getting image encoders
        /// </summary>
        private static Dictionary<string, ImageCodecInfo> encoders = null;

        /// <summary>
        /// A quick lookup for getting image encoders
        /// </summary>
        public static Dictionary<string, ImageCodecInfo> Encoders
        {
            //get accessor that creates the dictionary on demand
            get
            {
                //if the quick lookup isn't initialised, initialise it
                if (encoders == null)
                {
                    encoders = new Dictionary<string, ImageCodecInfo>();
                }

                //if there are no codecs, try loading them
                if (encoders.Count == 0)
                {
                    //get all the codecs
                    foreach (ImageCodecInfo codec in ImageCodecInfo.GetImageEncoders())
                    {
                        //add each codec to the quick lookup
                        encoders.Add(codec.MimeType.ToLower(), codec);
                    }
                }

                //return the lookup
                return encoders;
            }
        }

        /// <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 System.Drawing.Bitmap ResizeImage(System.Drawing.Image image, int width, int height)
        {
            //a holder for the result
            Bitmap result = new Bitmap(width, height);

            //use a graphics object to draw the resized image into the bitmap
            using (Graphics graphics = Graphics.FromImage(result))
            {
                //set the resize quality modes to high quality
                graphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
                graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                //draw the image into the target bitmap
                graphics.DrawImage(image, 0, 0, result.Width, result.Height);
            }

            //return the resulting bitmap
            return result;
        }

        /// <summary> 
        /// Saves an image as a jpeg image, with the given quality 
        /// </summary> 
        /// <param name="path">Path to which the image would be saved.</param> 
        /// <param name="quality">An integer from 0 to 100, with 100 being the 
        /// highest quality</param> 
        /// <exception cref="ArgumentOutOfRangeException">
        /// An invalid value was entered for image quality.
        /// </exception>
        public static void SaveJpeg(string path, Image image, int quality)
        {
            //ensure the quality is within the correct range
            if ((quality < 0) || (quality > 100))
            {
                //create the error message
                string error = string.Format("Jpeg image quality must be between 0 and 100, with 100 being the highest quality.  A value of {0} was specified.", quality);
                //throw a helpful exception
                throw new ArgumentOutOfRangeException(error);
            }

            //create an encoder parameter for the image quality
            EncoderParameter qualityParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);
            //get the jpeg codec
            ImageCodecInfo jpegCodec = GetEncoderInfo("image/jpeg");

            //create a collection of all parameters that we will pass to the encoder
            EncoderParameters encoderParams = new EncoderParameters(1);
            //set the quality parameter for the codec
            encoderParams.Param[0] = qualityParam;
            //save the image using the codec and the parameters
            image.Save(path, jpegCodec, encoderParams);
        }

        /// <summary> 
        /// Returns the image codec with the given mime type 
        /// </summary> 
        public static ImageCodecInfo GetEncoderInfo(string mimeType)
        {
            //do a case insensitive search for the mime type
            string lookupKey = mimeType.ToLower();

            //the codec to return, default to null
            ImageCodecInfo foundCodec = null;

            //if we have the encoder, get it to return
            if (Encoders.ContainsKey(lookupKey))
            {
                //pull the codec from the lookup
                foundCodec = Encoders[lookupKey];
            }

            return foundCodec;
        } 
    }
}

Answer 8

This is an article I spotted being referenced in Paint.NET's code for image resampling: Various Simple Image Processing Techniques by Paul Bourke.

Answer 9

you could try this one if it's a lowres cgi 2D Image Filter