c# - 高质量图像缩放库

Question

我想以与 Photoshop 一样好的质量水平在 C# 中缩放图像。有没有可用的 C# 图像处理库来做这件事？

score 234 · Accepted Answer

这是一个注释很好的 Image Manipulation 帮助器类，您可以查看和使用它。我将其编写为如何在 C# 中执行某些图像处理任务的示例。您将对采用 System.Drawing.Image、宽度和高度作为参数的ResizeImage函数感兴趣。

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 lock to prevent concurrency issues loading the encoders.
        /// </summary>
        private static object encodersLock = new object();

        /// <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)
                {
                    //protect against concurrency issues
                    lock (encodersLock)
                    {
                        //check again, we might not have been the first person to acquire the lock (see the double checked lock pattern)
                        if (encoders == null)
                        {
                            encoders = new Dictionary<string, ImageCodecInfo>();

                            //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);
            //set the resolutions the same to avoid cropping due to resolution differences
            result.SetResolution(image.HorizontalResolution, image.VerticalResolution);

            //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;
        } 
    }
}

更新

一些人一直在评论中询问如何使用 ImageUtilities 类的示例，所以你开始吧。

//resize the image to the specified height and width
using (var resized = ImageUtilities.ResizeImage(image, 50, 100))
{
    //save the resized image as a jpeg with a quality of 90
    ImageUtilities.SaveJpeg(@"C:\myimage.jpeg", resized, 90);
}

笔记

请记住，图像是一次性的，因此您需要将调整大小的结果分配给 using 声明（或者您可以使用 try finally 并确保在 finally 中调用 dispose）。

score 15 · Accepted Answer

在我看来，当您使用 GDI+ 绘制图像时，它的缩放比例非常好。您可以使用它来创建缩放图像。

如果你想用 GDI+ 缩放你的图像，你可以这样做：

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));
}

score 10 · Accepted Answer

Imagemagick和GD等经过测试的库可用于 .NET

您还可以阅读诸如双三次插值之类的内容并编写自己的内容。

score 8 · Accepted Answer

CodeProject 文章讨论和分享缩放图像的源代码：

score 6 · Accepted Answer

使用这个库：http: //imageresizing.net

阅读图书馆作者的这篇文章：20 Image Sizing Pitfalls with .NET

score 4 · Accepted Answer

尝试 Graphics.InterpolationMode 的不同值。GDI+ 中有几种典型的缩放算法可用。如果其中一个足以满足您的需要，您可以走这条路，而不是依赖外部库。

score 3 · Accepted Answer

您可以尝试dotImage，这是我公司的产品之一，它包括一个用于重采样图像的对象，该对象具有18 种过滤器类型，用于各种质量级别。

典型用法是：

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

此外，dotImage 包含 140 个奇怪的图像处理命令，其中包括许多类似于 PhotoShop 中的过滤器，如果您正在寻找的话。

score 2 · Accepted Answer

这可能会有所帮助

    public Image ResizeImage(Image source, RectangleF destinationBounds)
    {
        RectangleF sourceBounds = new RectangleF(0.0f,0.0f,(float)source.Width, (float)source.Height);
        RectangleF scaleBounds = new RectangleF();

        Image destinationImage = new Bitmap((int)destinationBounds.Width, (int)destinationBounds.Height);
        Graphics graph = Graphics.FromImage(destinationImage);
        graph.InterpolationMode =
            System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

        // Fill with background color
        graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), destinationBounds);

        float resizeRatio, sourceRatio;
        float scaleWidth, scaleHeight;

        sourceRatio = (float)source.Width / (float)source.Height;

        if (sourceRatio >= 1.0f)
        {
            //landscape
            resizeRatio = destinationBounds.Width / sourceBounds.Width;
            scaleWidth = destinationBounds.Width;
            scaleHeight = sourceBounds.Height * resizeRatio;
            float trimValue = destinationBounds.Height - scaleHeight;
            graph.DrawImage(source, 0, (trimValue / 2), destinationBounds.Width, scaleHeight);
        }
        else
        {
            //portrait
            resizeRatio = destinationBounds.Height/sourceBounds.Height;
            scaleWidth = sourceBounds.Width * resizeRatio;
            scaleHeight = destinationBounds.Height;
            float trimValue = destinationBounds.Width - scaleWidth;
            graph.DrawImage(source, (trimValue / 2), 0, scaleWidth, destinationBounds.Height);
        }

        return destinationImage;

    }

请注意InterpolationMode.HighQualityBicubic-> 这通常是性能和结果之间的良好折衷。

score 1 · Accepted Answer

试试这个基本的代码片段：

private static Bitmap ResizeBitmap(Bitmap srcbmp, int width, int height )
{
    Bitmap newimage = new Bitmap(width, height);
    using (Graphics g = Graphics.FromImage(newimage))
           g.DrawImage(srcbmp, 0, 0, width, height);
    return newimage;
}

score 0 · Accepted Answer

有一篇关于 Code Project的文章关于使用 GDI+ for .NET 使用双三次插值来调整照片大小。

在另一个博客上也有关于这个主题的另一篇文章（我认为是 MS 员工），但我在任何地方都找不到链接。:(也许其他人可以找到它？

score 0 · Accepted Answer

这是我发现在 Paint.NET 的图像重采样代码中引用的一篇文章： Paul Bourke 的各种简单图像处理技术。

score 0 · Accepted Answer

0

如果它是低分辨率 cgi 2D 图像过滤器，你可以试试这个

于 2010-05-27T08:47:10.450 回答

score 0 · Accepted Answer

你可以试试魔法内核。与双三次重采样相比，它在放大时产生的像素化伪影更少，并且在缩小时也能提供非常好的结果。源代码可从网站以 c# 形式获得。

score 0 · Accepted Answer

我对琼斯医生的回答有一些改进。

它适用于想要如何按比例调整图像大小的人。它测试并为我工作。

我添加的类的方法：

public static System.Drawing.Bitmap ResizeImage(System.Drawing.Image image, Size size)
{
    return ResizeImage(image, size.Width, size.Height);
}


public static Size GetProportionedSize(Image image, int maxWidth, int maxHeight, bool withProportion)
{
    if (withProportion)
    {
        double sourceWidth = image.Width;
        double sourceHeight = image.Height;

        if (sourceWidth < maxWidth && sourceHeight < maxHeight)
        {
            maxWidth = (int)sourceWidth;
            maxHeight = (int)sourceHeight;
        }
        else
        {
            double aspect = sourceHeight / sourceWidth;

            if (sourceWidth < sourceHeight)
            {
                maxWidth = Convert.ToInt32(Math.Round((maxHeight / aspect), 0));
            }
            else
            {
                maxHeight = Convert.ToInt32(Math.Round((maxWidth * aspect), 0));
            }
        }
    }

    return new Size(maxWidth, maxHeight);
}

根据此代码使用新的可用：

using (var resized = ImageUtilities.ResizeImage(image, ImageUtilities.GetProportionedSize(image, 50, 100)))
{
    ImageUtilities.SaveJpeg(@"C:\myimage.jpeg", resized, 90);
}

c# - 高质量图像缩放库

14 回答 14

更新

笔记

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