如何调整图像的大小 C#

Question

因为Size 、 Width和Height是System.Drawing.Image Get()属性；
如何在运行时在 C# 中调整 Image 对象的大小？

现在，我只是使用以下方法创建一个新Image ：

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

Answer 1

这将执行高质量的调整大小：

/// <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;
}

• wrapMode.SetWrapMode(WrapMode.TileFlipXY)防止图像边界周围出现重影——天真的调整大小将采样超出图像边界的透明像素，但通过镜像图像我们可以获得更好的样本（这个设置非常明显）
• destImage.SetResolution不论物理尺寸如何都保持 DPI -- 在缩小图像尺寸或打印时可能会提高质量
• 合成控制像素与背景的混合方式——可能不需要，因为我们只绘制一件事。
  • graphics.CompositingMode确定源图像中的像素是覆盖还是与背景像素组合。 SourceCopy指定在呈现颜色时，它会覆盖背景颜色。
  • graphics.CompositingQuality决定了分层图像的渲染质量级别。
• graphics.InterpolationMode确定如何计算两个端点之间的中间值
• graphics.SmoothingMode指定线条、曲线和填充区域的边缘是否使用平滑（也称为抗锯齿）——可能仅适用于矢量
• graphics.PixelOffsetMode影响绘制新图像时的渲染质量

保持纵横比留给读者作为练习（实际上，我只是不认为这个功能的工作是为你做这件事）。

此外， 这是一篇很好的文章，描述了图像调整大小的一些陷阱。 上面的函数会覆盖大部分，但是你仍然需要担心保存.

Answer 2

不知道这有什么困难，做你正在做的事情，使用重载的 Bitmap 构造函数来创建一个重新调整大小的图像，你唯一缺少的是转换回 Image 数据类型：

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

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

Answer 3

在这个问题中，你会得到一些答案，包括我的：

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;
}

Answer 4

为什么不使用System.Drawing.Image.GetThumbnailImage方法？

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

示例：

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);

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

Answer 5

你可以试试净贵宾，在C＃绑定libvips 。 它是一个懒惰的、流式的、需求驱动的图像处理库，因此它可以在不需要加载整个图像的情况下进行这样的操作。

例如，它带有一个方便的图像缩略图：

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

它还支持智能裁剪，一种智能确定图像最重要部分并在裁剪图像时保持焦点的方式。 例如：

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

其中owl.jpg是一个偏离中心的合成：

给出了这个结果：

首先它缩小图像以将垂直轴缩小到 128 像素，然后使用attention策略将其缩小到 128 像素。 这个在图像中搜索可能会Smartcrop()眼的特征，有关详细信息，请参阅Smartcrop() 。

Answer 6

public static Image resizeImage(Image image, int new_height, int new_width)
{
    Bitmap new_image = new Bitmap(new_width, new_height);
    Graphics g = Graphics.FromImage((Image)new_image );
    g.InterpolationMode = InterpolationMode.High;
    g.DrawImage(image, 0, 0, new_width, new_height);
    return new_image;
}

Answer 7

这将——

• 无需循环即可调整宽度和高度
• 不超过图片原始尺寸

/////////////

private void ResizeImage(Image img, double maxWidth, double maxHeight)
{
    double resizeWidth = img.Source.Width;
    double resizeHeight = img.Source.Height;

    double aspect = resizeWidth / resizeHeight;

    if (resizeWidth > maxWidth)
    {
        resizeWidth = maxWidth;
        resizeHeight = resizeWidth / aspect;
    }
    if (resizeHeight > maxHeight)
    {
        aspect = resizeWidth / resizeHeight;
        resizeHeight = maxHeight;
        resizeWidth = resizeHeight * aspect;
    }

    img.Width = resizeWidth;
    img.Height = resizeHeight;
}

Answer 8

此代码与上述答案之一发布的代码相同..但会将透明像素转换为白色而不是黑色......谢谢:)

    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.White);
        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;
    }

Answer 9

在我制作的应用程序中，有必要创建一个具有多个选项的函数。 它相当大，但它可以调整图像大小，可以保持纵横比并且可以切割边缘以仅返回图像的中心：

/// <summary>
    /// Resize image with a directory as source
    /// </summary>
    /// <param name="OriginalFileLocation">Image location</param>
    /// <param name="heigth">new height</param>
    /// <param name="width">new width</param>
    /// <param name="keepAspectRatio">keep the aspect ratio</param>
    /// <param name="getCenter">return the center bit of the image</param>
    /// <returns>image with new dimentions</returns>
    public Image resizeImageFromFile(String OriginalFileLocation, int heigth, int width, Boolean keepAspectRatio, Boolean getCenter)
    {
        int newheigth = heigth;
        System.Drawing.Image FullsizeImage = System.Drawing.Image.FromFile(OriginalFileLocation);

        // Prevent using images internal thumbnail
        FullsizeImage.RotateFlip(System.Drawing.RotateFlipType.Rotate180FlipNone);
        FullsizeImage.RotateFlip(System.Drawing.RotateFlipType.Rotate180FlipNone);

        if (keepAspectRatio || getCenter)
        {
            int bmpY = 0;
            double resize = (double)FullsizeImage.Width / (double)width;//get the resize vector
            if (getCenter)
            {
                bmpY = (int)((FullsizeImage.Height - (heigth * resize)) / 2);// gives the Y value of the part that will be cut off, to show only the part in the center
                Rectangle section = new Rectangle(new Point(0, bmpY), new Size(FullsizeImage.Width, (int)(heigth * resize)));// create the section to cut of the original image
                //System.Console.WriteLine("the section that will be cut off: " + section.Size.ToString() + " the Y value is minimized by: " + bmpY);
                Bitmap orImg = new Bitmap((Bitmap)FullsizeImage);//for the correct effect convert image to bitmap.
                FullsizeImage.Dispose();//clear the original image
                using (Bitmap tempImg = new Bitmap(section.Width, section.Height))
                {
                    Graphics cutImg = Graphics.FromImage(tempImg);//              set the file to save the new image to.
                    cutImg.DrawImage(orImg, 0, 0, section, GraphicsUnit.Pixel);// cut the image and save it to tempImg
                    FullsizeImage = tempImg;//save the tempImg as FullsizeImage for resizing later
                    orImg.Dispose();
                    cutImg.Dispose();
                    return FullsizeImage.GetThumbnailImage(width, heigth, null, IntPtr.Zero);
                }
            }
            else newheigth = (int)(FullsizeImage.Height / resize);//  set the new heigth of the current image
        }//return the image resized to the given heigth and width
        return FullsizeImage.GetThumbnailImage(width, newheigth, null, IntPtr.Zero);
    }

为了更容易访问该函数，可以添加一些重载函数：

/// <summary>
    /// Resize image with a directory as source
    /// </summary>
    /// <param name="OriginalFileLocation">Image location</param>
    /// <param name="heigth">new height</param>
    /// <param name="width">new width</param>
    /// <returns>image with new dimentions</returns>
    public Image resizeImageFromFile(String OriginalFileLocation, int heigth, int width)
    {
        return resizeImageFromFile(OriginalFileLocation, heigth, width, false, false);
    }

    /// <summary>
    /// Resize image with a directory as source
    /// </summary>
    /// <param name="OriginalFileLocation">Image location</param>
    /// <param name="heigth">new height</param>
    /// <param name="width">new width</param>
    /// <param name="keepAspectRatio">keep the aspect ratio</param>
    /// <returns>image with new dimentions</returns>
    public Image resizeImageFromFile(String OriginalFileLocation, int heigth, int width, Boolean keepAspectRatio)
    {
        return resizeImageFromFile(OriginalFileLocation, heigth, width, keepAspectRatio, false);
    }

现在是最后两个可选设置的布尔值。 像这样调用函数：

System.Drawing.Image ResizedImage = resizeImageFromFile(imageLocation, 800, 400, true, true);

Answer 10

public string CreateThumbnail(int maxWidth, int maxHeight, string path)
{

    var image = System.Drawing.Image.FromFile(path);
    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);
    Graphics thumbGraph = Graphics.FromImage(newImage);

    thumbGraph.CompositingQuality = CompositingQuality.HighQuality;
    thumbGraph.SmoothingMode = SmoothingMode.HighQuality;
    //thumbGraph.InterpolationMode = InterpolationMode.HighQualityBicubic;

    thumbGraph.DrawImage(image, 0, 0, newWidth, newHeight);
    image.Dispose();

    string fileRelativePath = "newsizeimages/" + maxWidth + Path.GetFileName(path);
    newImage.Save(Server.MapPath(fileRelativePath), newImage.RawFormat);
    return fileRelativePath;
}

点击这里http://bhupendrasinghsaini.blogspot.in/2014/07/resize-image-in-c.html

Answer 11

这是我针对特定要求制定的代码，即：目的地始终处于横向比例。 它应该给你一个良好的开端。

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;

}

Answer 12

如果您正在使用BitmapSource ：

var resizedBitmap = new TransformedBitmap(
    bitmapSource,
    new ScaleTransform(scaleX, scaleY));

如果您想更好地控制质量，请先运行：

RenderOptions.SetBitmapScalingMode(
    bitmapSource,
    BitmapScalingMode.HighQuality);

（默认为BitmapScalingMode.Linear相当于BitmapScalingMode.LowQuality 。）

Answer 13

我使用 ImageProcessorCore，主要是因为它适用于 .Net Core。

它还有更多选项，例如转换类型、裁剪图像等

http://imageprocessor.org/imageprocessor/

Answer 14

您可以为此使用Accord.NET 框架。 它提供了几种不同的调整大小的方法：

• 双三次
• 双线性
• 最近邻

Answer 15

使用下面的函数和下面的例子来改变图像大小：

//Example : 
System.Net.Mime.MediaTypeNames.Image newImage = System.Net.Mime.MediaTypeNames.Image.FromFile("SampImag.jpg");
System.Net.Mime.MediaTypeNames.Image temImag = FormatImage(newImage, 100, 100);

//image size modification unction   
public static System.Net.Mime.MediaTypeNames.Image FormatImage(System.Net.Mime.MediaTypeNames.Image img, int outputWidth, int outputHeight)
{

    Bitmap outputImage = null;
    Graphics graphics = null;
    try
    {
         outputImage = new Bitmap(outputWidth, outputHeight, System.Drawing.Imaging.PixelFormat.Format16bppRgb555);
         graphics = Graphics.FromImage(outputImage);
         graphics.DrawImage(img, new Rectangle(0, 0, outputWidth, outputHeight),
         new Rectangle(0, 0, img.Width, img.Height), GraphicsUnit.Pixel);

         return outputImage;
     }
     catch (Exception ex)
     {
           return img;
     }
}

Answer 16

注意：这不适用于 ASP.Net Core，因为 WebImage 依赖于 System.Web，但在以前版本的 ASP.Net 上，我多次使用此代码段并且很有用。

String ThumbfullPath = Path.GetFileNameWithoutExtension(file.FileName) + "80x80.jpg";
var ThumbfullPath2 = Path.Combine(ThumbfullPath, fileThumb);
using (MemoryStream stream = new MemoryStream(System.IO.File.ReadAllBytes(fullPath)))
{
      var thumbnail = new WebImage(stream).Resize(80, 80);
      thumbnail.Save(ThumbfullPath2, "jpg");
}

Answer 17

调整大小并保存图像以适应宽度和高度，就像保持图像比例的画布

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;

namespace Infra.Files
{
    public static class GenerateThumb
    {
        /// <summary>
        /// Resize and save an image to fit under width and height like a canvas keeping things proportional
        /// </summary>
        /// <param name="originalImagePath"></param>
        /// <param name="thumbImagePath"></param>
        /// <param name="newWidth"></param>
        /// <param name="newHeight"></param>
        public static void GenerateThumbImage(string originalImagePath, string thumbImagePath, int newWidth, int newHeight)
        {
            Bitmap srcBmp = new Bitmap(originalImagePath);
            float ratio = 1;
            float minSize = Math.Min(newHeight, newHeight);

            if (srcBmp.Width > srcBmp.Height)
            {
                ratio = minSize / (float)srcBmp.Width;
            }
            else
            {
                ratio = minSize / (float)srcBmp.Height;
            }

            SizeF newSize = new SizeF(srcBmp.Width * ratio, srcBmp.Height * ratio);
            Bitmap target = new Bitmap((int)newSize.Width, (int)newSize.Height);

            using (Graphics graphics = Graphics.FromImage(target))
            {
                graphics.CompositingQuality = CompositingQuality.HighSpeed;
                graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
                graphics.CompositingMode = CompositingMode.SourceCopy;
                graphics.DrawImage(srcBmp, 0, 0, newSize.Width, newSize.Height);

                using (MemoryStream memoryStream = new MemoryStream())
                {
                    target.Save(thumbImagePath);
                }
            }
        }
    }
}

Answer 18

下面的函数将返回显示图像的新大小。这在这里可能没有帮助。但它会返回调整后的显示矩形大小。

 public static  class ResizeImage
{
    /// <summary>
    /// Return new resized size to display the image
    /// </summary>
    /// <param name="srcrectanle">source rectangle of image or you can pass the bitmap and set the size accrodingly</param>
    /// <param name="initSize">initial size of the page to draw image</param>
    /// <returns></returns>
    public static SizeF getResizedRectangle(RectangleF srcrectanle, SizeF initSize)
    {
        float sw = srcrectanle.Width;
        float sh = srcrectanle.Height;
        float dw = initSize.Width;
        float dh = initSize.Height;
        float finalHeight, finalWidth;
        float Sourceratio = sw / sh;

        if (Sourceratio >= 1)
        {
            finalWidth = (int)dw;
            float ratio = sw / dw;
            finalHeight = (sh / ratio);
        }
        else
        {
            finalHeight = (int)dh;
            float ratio = sh / dh;
            finalWidth = (sw / ratio);
        }
        return new SizeF(finalHeight, finalHeight);


    }
}