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C#图像缩放以保持纵横比的不同大小

c#image-processingsystem.drawingimage-scaling
105

我正在尝试调整图片的大小，同时保留原始图像的宽高比，以便新图像不会变形。

例如：

将一个 150*100 的图像转换为一个 150*150 的图像。
高度的额外 50 像素需要使用白色背景颜色填充。

这是我目前正在使用的代码。

它可以成功地调整大小，但改变原始图像的宽高比会使新图像变形。

private void resizeImage(string path, string originalFilename, 
                         int width, int height)
    {
        Image image = Image.FromFile(path + originalFilename);

        System.Drawing.Image thumbnail = new Bitmap(width, height);
        System.Drawing.Graphics graphic = 
                     System.Drawing.Graphics.FromImage(thumbnail);

        graphic.InterpolationMode = InterpolationMode.HighQualityBicubic;
        graphic.SmoothingMode = SmoothingMode.HighQuality;
        graphic.PixelOffsetMode = PixelOffsetMode.HighQuality;
        graphic.CompositingQuality = CompositingQuality.HighQuality;

        graphic.DrawImage(image, 0, 0, width, height);

        System.Drawing.Imaging.ImageCodecInfo[] info =
                         ImageCodecInfo.GetImageEncoders();
        EncoderParameters encoderParameters;
        encoderParameters = new EncoderParameters(1);
        encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality,
                         100L);            
        thumbnail.Save(path + width + "." + originalFilename, info[1], 
                         encoderParameters);
    }

编辑：我希望图像被填充而不是裁剪

14个回答
1
保持画面比例，消除黑边和白边。
static Image FixedSize(Image imgPhoto, int Width, int Height)
    {
        int sourceWidth = imgPhoto.Width;
        int sourceHeight = imgPhoto.Height;
        int X = 0;
        int Y = 0;

        float nPercent = 0;
        float nPercentW = 0;
        float nPercentH = 0;

        nPercentW = ((float)Width / (float)sourceWidth);
        nPercentH = ((float)Height / (float)sourceHeight);
        if (nPercentH < nPercentW)
        {
            nPercent = nPercentH;
        }
        else
        {
            nPercent = nPercentW;
        }

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

        Bitmap bmPhoto = new Bitmap(destWidth, destHeight, PixelFormat.Format24bppRgb);

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

        Graphics grPhoto = Graphics.FromImage(bmPhoto);

        grPhoto.DrawImage(imgPhoto,
                new Rectangle(X, Y, destWidth, destHeight),
                new Rectangle(X, Y, sourceWidth, sourceHeight),
                GraphicsUnit.Pixel);

        grPhoto.Dispose();
        return bmPhoto;
    }
1
public static void resizeImage_n_save(Stream sourcePath, string targetPath, int requiredSize)
    {
        using (var image = System.Drawing.Image.FromStream(sourcePath))
        {
            double ratio = 0;

            var newWidth = 0;
            var newHeight = 0;
            double w = Convert.ToInt32(image.Width);
            double h = Convert.ToInt32(image.Height);
            if (w > h)
            {
                ratio = h / w * 100;
                newWidth = requiredSize;
                newHeight = Convert.ToInt32(requiredSize * ratio / 100);
            }
            else
            {
                ratio = w / h * 100;
                newHeight = requiredSize;
                newWidth = Convert.ToInt32(requiredSize * ratio / 100);
            }

            //   var newWidth = (int)(image.Width * scaleFactor);
            // var newHeight = (int)(image.Height * scaleFactor);
            var thumbnailImg = new Bitmap(newWidth, newHeight);
            var thumbGraph = Graphics.FromImage(thumbnailImg);
            thumbGraph.CompositingQuality = CompositingQuality.HighQuality;
            thumbGraph.SmoothingMode = SmoothingMode.HighQuality;
            thumbGraph.InterpolationMode = InterpolationMode.HighQualityBicubic;
            var imageRectangle = new Rectangle(0, 0, newWidth, newHeight);

            thumbGraph.DrawImage(image, imageRectangle);
            thumbnailImg.Save(targetPath, image.RawFormat);

            //var img = FixedSize(image, requiredSize, requiredSize);
            //img.Save(targetPath, image.RawFormat);

        }
    }
0

我写这篇文章是因为这里已有的答案都不够简单。您可以将硬编码的128替换为任何您想要的值，或者基于原始图像的大小进行计算。我只想将图像重新缩放为128x128的图像，保持其宽高比并将结果居中显示在新图像中。

    private Bitmap CreateLargeIconForImage(Bitmap src)
    {
        Bitmap bmp = new Bitmap(128, 128);
        Graphics g = Graphics.FromImage(bmp);

        float scale = Math.Max((float)src.Width / 128.0f, (float)src.Height / 128.0f);
        PointF p = new PointF(128.0f - ((float)src.Width / scale), 128.0f - ((float)src.Height / scale));
        SizeF size = new SizeF((float)src.Width / scale, (float)src.Height / scale);

        g.DrawImage(src, new RectangleF(p, size));

        return bmp;
    }
0

我知道这是一个较旧的帖子。然而，这是在谷歌搜索该主题时的第一个结果。 没有任何答案符合我的要求。因此，我通过理解早期的解决方案，但将结果图像大小限制为最适合的高度和宽度，提供了一个解决方案。

        double ratioW = (double)desiredWidthPixels / (double)originalImage.Width;
        double ratioH = (double)desiredHeightPixels / (double)originalImage.Height;
        double ratio = ratioW < ratioH ? ratioW : ratioH;
        int suitableWidth = (int)(originalImage.Width * ratio);
        int suitableHeight = (int)(originalImage.Height * ratio);

        var resizedPhoto = new Bitmap((int)suitableWidth, (int)suitableHeight);
        var graphicsSurface = Graphics.FromImage(resizedPhoto);
        graphicsSurface.DrawImage(originalImage, new RectangleF(new PointF(0,0), new SizeF(suitableWidth, suitableHeight)));
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