将大图像压缩为小格式

Question

我将图像以二进制形式存储在数据库中，为了向它们展示我想将它们压缩成较小的图像 (4000 x 3000) 到 (400 x 300)，这基本上可以工作，但是图像看起来很棒，有人可以指点我吗向正确的方向？

我现在在用：

System.IO.MemoryStream myMemStream = new System.IO.MemoryStream(bytes);
        System.Drawing.Image fullsizeImage = System.Drawing.Image.FromStream(myMemStream);
        Type typeoff = fullsizeImage.GetType();
        double height = fullsizeImage.Height;
        double width = Convert.ToDouble(fullsizeImage.Width);
        double aspect = setWidth / width;
        setHeight = Convert.ToInt32(aspect * height);
        System.Drawing.Image newImage = fullsizeImage.GetThumbnailImage(Convert.ToInt32(setWidth), setHeight, null, IntPtr.Zero);
        System.IO.MemoryStream myResult = new System.IO.MemoryStream();
        using (System.IO.MemoryStream imageMemStream = new System.IO.MemoryStream(bytes))
        {
            using (Bitmap bitmap = new Bitmap(imageMemStream))
            {
                ImageFormat imageFormat = bitmap.RawFormat;
                if (bitmap.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Jpeg))
                {
                    newImage.Save(myResult, System.Drawing.Imaging.ImageFormat.Jpeg);
                }
                if (bitmap.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Gif))
                {
                    newImage.Save(myResult, System.Drawing.Imaging.ImageFormat.Gif);
                }
                if (bitmap.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Bmp))
                {
                    newImage.Save(myResult, System.Drawing.Imaging.ImageFormat.Bmp);
                }
                if (bitmap.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Png))
                {
                    newImage.Save(myResult, System.Drawing.Imaging.ImageFormat.Png);
                }
                if (bitmap.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Icon))
                {
                    newImage.Save(myResult, System.Drawing.Imaging.ImageFormat.Icon);
                }
            }
        }
        _bytes = myResult.ToArray();  //Returns a new byte array.

一直在寻找这个，但还不知道如何用我的二进制输入和输出来实现它：

        Bitmap image = new Bitmap(fullsizeImage, Convert.ToInt32(newWidth), setHeight);
        using (Graphics gr = Graphics.FromImage(image))
        {
            gr.SmoothingMode = SmoothingMode.HighQuality;
            gr.InterpolationMode = InterpolationMode.HighQualityBicubic;
            gr.PixelOffsetMode = PixelOffsetMode.HighQuality;
            gr.DrawImage(fullsizeImage, new Rectangle(0, 0, Convert.ToInt32(newWidth), setHeight));
            _bytes = gr.T.ToArray();
        }

可能我做错了什么，但不知道从哪里做起，在图像压缩方面没有太多经验。

如有任何帮助，我们将不胜感激

更新

试图从图像中提取 mime 类型但不是很幸运得到它，使用这个并且找不到任何其他的，代码有一个空值 return。

public byte[] imageToByteArray(System.Drawing.Image newImage)
    {

        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        ImageFormat format = newImage.RawFormat;
        if (ImageCodecInfo.GetImageDecoders().FirstOrDefault(c => c.FormatID == format.Guid) != null)
        {
            ImageCodecInfo codec = ImageCodecInfo.GetImageDecoders().FirstOrDefault(c => c.FormatID == format.Guid);
            string mimeType = codec.MimeType;
        }
        newImage.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
        return ms.ToArray();

Answer 1

您可以使用此函数创建简化的 Images:

public static Image ShrinkImage(Image original, int scale)
{
    Bitmap bmp = new Bitmap(original.Width / scale, original.Height / scale,
                            original.PixelFormat);
    using (Graphics G = Graphics.FromImage(bmp))
    {
        G.InterpolationMode = InterpolationMode.HighQualityBicubic;
        G.SmoothingMode = SmoothingMode.HighQuality;
        Rectangle srcRect = new Rectangle(0,0,original.Width, original.Height);
        Rectangle destRect = new Rectangle(0,0,bmp.Width, bmp.Height);
        G.DrawImage(original, destRect, srcRect, GraphicsUnit.Pixel);
        bmp.SetResolution( original.HorizontalResolution, original.VerticalResolution);
    }
    return (Image)bmp;
}

请注意，它仅适用于真正的 Bitmap Images，不适用于 Icons；但是无论如何尝试减少图标是没有意义的！

另请注意，您可能想要也可能不想更改新图像的 Dpi。在代码中我没有，但也许你想扩大它或将它设置为固定值..

不要忘记Dispose你的Images，当你用完它们！

将大图像压缩为小格式

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