C# 创建缩略图（低质量和大尺寸问题）

发布于 2024-09-01 19:53:04 字数 1059 浏览 3 评论 0原文

public void CreateThumbnail(Image img1, Photo photo, string targetDirectoryThumbs)
        {
            int newWidth = 700;
            int newHeight = 700;
            double ratio = 0;

            if (img1.Width > img1.Height)
            {
                ratio = img1.Width / (double)img1.Height;
                newHeight = (int)(newHeight / ratio);
            }
            else
            {
                ratio = img1.Height / (double)img1.Width;
                newWidth = (int)(newWidth / ratio);
            }

            Image bmp1 = img1.GetThumbnailImage(newWidth, newHeight, null, IntPtr.Zero);
            bmp1.Save(targetDirectoryThumbs + photo.PhotoID + ".jpg");

            img1.Dispose();
            bmp1.Dispose();
        }

我设置了 700px 以便您可以更好地了解问题。这是原始图像和调整大小 1。

有什么好的推荐吗？

谢谢，
岛

原文

public void CreateThumbnail(Image img1, Photo photo, string targetDirectoryThumbs)
        {
            int newWidth = 700;
            int newHeight = 700;
            double ratio = 0;

            if (img1.Width > img1.Height)
            {
                ratio = img1.Width / (double)img1.Height;
                newHeight = (int)(newHeight / ratio);
            }
            else
            {
                ratio = img1.Height / (double)img1.Width;
                newWidth = (int)(newWidth / ratio);
            }

            Image bmp1 = img1.GetThumbnailImage(newWidth, newHeight, null, IntPtr.Zero);
            bmp1.Save(targetDirectoryThumbs + photo.PhotoID + ".jpg");

            img1.Dispose();
            bmp1.Dispose();
        }

I've put 700px so that you can have better insight of the problem.
Here is original image and resized one.

Any good recommendation?

Thanks,
Ile

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香草可樂 2024-09-08 19:53:04

您应该会发现我对这个问题的回答很有帮助。它包括一个用 C# 进行高质量图像缩放的示例。

我的其他答案中的完整示例包括如何将图像保存为 jpeg。

这是相关的代码...

    /// <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); 

        //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; 
    }

You should find my answer to this question helpful. It includes a sample for high quality image scaling in C#.

The full sample in my other answer includes how to save the image as a jpeg.

Here's the relevant bit of code...

    /// <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); 

        //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; 
    }

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枕头说它不想醒 2024-09-08 19:53:04

如果图像包含缩略图，它会自动将其拉伸到所需的大小...这会让它看起来像垃圾（就像你的情况;））

直接从 MSDN 中...

如果图像包含嵌入的
缩略图，此方法检索
嵌入的缩略图并对其进行缩放
到要求的尺寸。如果图像
不包含嵌入的缩略图
图像，此方法创建缩略图
通过缩放主图像来生成图像。

在你的情况下，我只是仔细检查了源图像的缩略图并得到了这个......

新的Windows缩略图：JPEG格式（偏移：830大小：3234）
缩略图类型：JPEG
缩略图宽度：112
缩略图高度：84

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往事风中埋 2024-09-08 19:53:04

尝试将原始图像绘制到另一个较小的图像上，并保存结果。

Bitmap bmp1 = new Bitmap(newWidth, newHeight);
Graphics g = Graphics.FromImage(bmp);
g.DrawImage(img1, 0, 0, newWidth, newHeight);
bmp1.Save(targetDirectoryThumbs + photo.PhotoID + ".jpg", ImageFormat.Jpeg);

Try to draw the original image to another smaller image, and save the result.

Bitmap bmp1 = new Bitmap(newWidth, newHeight);
Graphics g = Graphics.FromImage(bmp);
g.DrawImage(img1, 0, 0, newWidth, newHeight);
bmp1.Save(targetDirectoryThumbs + photo.PhotoID + ".jpg", ImageFormat.Jpeg);

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