Graphics.DrawImage不会更改图像的大小

Question

我有一个功能，可以获取图像并调整其大小以适合画布，同时保持其纵横比。 此代码只是此答案中代码的略微修改版本： c＃在保留纵横比的同时将图像调整为不同大小

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

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。

有人看到一个明显的错误会导致这种情况发生吗？ 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

图片的尺寸在这里定义

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被更改。 换句话说，绘制图像根本不会改变其大小，它只是获取图像并将其按照您的意愿绘制在画布上。

Answer 2

图像调整大小功能，请参见以下链接

http://www.codeproject.com/Articles/30524/An-Easy-to-Use-Image-Resizing-and-Cropping-Control?msg=5203911#xx5203911xx

此链接内容可能对您有帮助