Graphics.DrawImage不会改变图像的大小

Question

我有一个功能,它接收图像并调整大小以适应画布,同时保持其纵横比.此代码只是此答案中代码的微小修改版本: c#图像调整大小到不同大小,同时保留纵横比

对于此示例,我的画布高度为642,我的画布宽度为823.

当我运行以下功能时,该行

graphic.DrawImage(image, posX, posY, newWidth, newHeight);

似乎对图像大小没有任何作用.进去:

Image.Height == 800, 
Image.Width == 1280.
newHeight = 514,
newWidth == 823

在运行graphic.DrawImage之后

Image.Height == 800, 
Image.Width == 1280.

如您所见,Image的高度和宽度保持不变.

有没有人看到会导致这种情况发生的明显错误？谢谢!

    private Bitmap resizeImage(Bitmap workingImage,
                         int canvasWidth, int canvasHeight)
    {
        Image image = (Bitmap)workingImage.Clone();

        System.Drawing.Image thumbnail =
            new Bitmap(canvasWidth, canvasHeight); 

        double ratioX = (double)canvasWidth / (double)workingImage.Width;
        double ratioY = (double)canvasHeight / (double)workingImage.Height;

        double ratio = ratioX < ratioY ? ratioX : ratioY;

        int newHeight = Convert.ToInt32((double)workingImage.Height * ratio);
        int newWidth = Convert.ToInt32((double)workingImage.Width * ratio);

        int posX = Convert.ToInt32((canvasWidth - ((double)workingImage.Width * ratio)) / 2);
        int posY = Convert.ToInt32((canvasHeight - ((double)workingImage.Height * ratio)) / 2);

        using (Graphics graphic = Graphics.FromImage(thumbnail))
        {
            graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
            graphic.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            graphic.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
            graphic.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;

            graphic.Clear(SystemColors.Control); 
            graphic.DrawImage(image, posX, posY, newWidth, newHeight); //<--- HERE
        }

        System.Drawing.Imaging.ImageCodecInfo[] info =
                         System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders();
        System.Drawing.Imaging.EncoderParameters encoderParameters;
        encoderParameters = new System.Drawing.Imaging.EncoderParameters(1);
        encoderParameters.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality,
                         100L);

        return workingImage;
    }

Answer 1

此处定义了图像的大小

Image image = (Bitmap)workingImage.Clone();

这个

graphic.DrawImage(image, posX, posY, newWidth, newHeight);

仅使用指定的参数绘制图像,但这并不意味着图像大小会发生变化.换句话说,绘制图像只是不会改变它的大小,它只是拍摄图像并根据需要将其绘制在画布上.