画質を損なうことなく、asp.netで画像のサイズを変更します

StackOverflow https://stackoverflow.com/questions/2319983

質問

私は、ユーザーがいずれかのJPEG、GIF、BMPまたはPNG画像をアップロードすることができていているASP.NET 3.5 Webアプリケーションを開発しています。アップロードされた画像の大きさは、その後103×32を大きい場合、私はいくつかのブログの記事や記事を読んで持っている103のx 32にアップロードされた画像のサイズを変更したい、ともコードサンプルのいくつかを試してみましたが、何も仕事の右には思いません。誰もがこれを行うことに成功していますか？

役に立ちましたか？

解決

私はこの方法をしばらく前に同じ問題aを持っていたし、それに対処します：

private Image RezizeImage(Image img, int maxWidth, int maxHeight)
{
    if(img.Height < maxHeight && img.Width < maxWidth) return img;
    using (img)
    {
        Double xRatio = (double)img.Width / maxWidth;
        Double yRatio = (double)img.Height / maxHeight;
        Double ratio = Math.Max(xRatio, yRatio);
        int nnx = (int)Math.Floor(img.Width / ratio);
        int nny = (int)Math.Floor(img.Height / ratio);
        Bitmap cpy = new Bitmap(nnx, nny, PixelFormat.Format32bppArgb);
        using (Graphics gr = Graphics.FromImage(cpy))
        {
            gr.Clear(Color.Transparent);

            // This is said to give best quality when resizing images
            gr.InterpolationMode = InterpolationMode.HighQualityBicubic;

            gr.DrawImage(img,
                new Rectangle(0, 0, nnx, nny),
                new Rectangle(0, 0, img.Width, img.Height),
                GraphicsUnit.Pixel);
        }
        return cpy;
    }

}

private MemoryStream BytearrayToStream(byte[] arr)
{
    return new MemoryStream(arr, 0, arr.Length);
}

private void HandleImageUpload(byte[] binaryImage)
{
    Image img = RezizeImage(Image.FromStream(BytearrayToStream(binaryImage)), 103, 32);
    img.Save("IMAGELOCATION.png", System.Drawing.Imaging.ImageFormat.Gif);
}

私は、これは最高の品質を得るための方法だったことを読みます。

他のヒント

このコードは、Iの使用です。これは、回転をサポートし、また、72dpiです@ 24ビットカラーのJPEG規格の画像解像度設定（デフォルトGDI +によってを96DPI @ 32ビットカラーで画像を保存します）。画像のサイズを変更する場合にも、いくつかの人々の経験という黒/グレーのボーダー問題を修正します。

/// <summary>
/// Resizes and rotates an image, keeping the original aspect ratio. Does not dispose the original
/// Image instance.
/// </summary>
/// <param name="image">Image instance</param>
/// <param name="width">desired width</param>
/// <param name="height">desired height</param>
/// <param name="rotateFlipType">desired RotateFlipType</param>
/// <returns>new resized/rotated Image instance</returns>
public static Image Resize(Image image, int width, int height, RotateFlipType rotateFlipType)
{
    // clone the Image instance, since we don't want to resize the original Image instance
    var rotatedImage = image.Clone() as Image;
    rotatedImage.RotateFlip(rotateFlipType);
    var newSize = CalculateResizedDimensions(rotatedImage, width, height);

    var resizedImage = new Bitmap(newSize.Width, newSize.Height, PixelFormat.Format32bppArgb);
    resizedImage.SetResolution(72, 72);

    using (var graphics = Graphics.FromImage(resizedImage))
    {
        // set parameters to create a high-quality thumbnail
        graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
        graphics.SmoothingMode = SmoothingMode.AntiAlias;
        graphics.CompositingQuality = CompositingQuality.HighQuality;
        graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;

        // use an image attribute in order to remove the black/gray border around image after resize
        // (most obvious on white images), see this post for more information:
        // http://www.codeproject.com/KB/GDI-plus/imgresizoutperfgdiplus.aspx
        using (var attribute = new ImageAttributes())
        {
            attribute.SetWrapMode(WrapMode.TileFlipXY);

            // draws the resized image to the bitmap
            graphics.DrawImage(rotatedImage, new Rectangle(new Point(0, 0), newSize), 0, 0, rotatedImage.Width, rotatedImage.Height, GraphicsUnit.Pixel, attribute);
        }
    }

    return resizedImage;
}

/// <summary>
/// Calculates resized dimensions for an image, preserving the aspect ratio.
/// </summary>
/// <param name="image">Image instance</param>
/// <param name="desiredWidth">desired width</param>
/// <param name="desiredHeight">desired height</param>
/// <returns>Size instance with the resized dimensions</returns>
private static Size CalculateResizedDimensions(Image image, int desiredWidth, int desiredHeight)
{
    var widthScale = (double)desiredWidth / image.Width;
    var heightScale = (double)desiredHeight / image.Height;

    // scale to whichever ratio is smaller, this works for both scaling up and scaling down
    var scale = widthScale < heightScale ? widthScale : heightScale;

    return new Size
                   {
                       Width = (int) (scale * image.Width),
                       Height = (int) (scale * image.Height)
                   };
}

次のようにビットマップの実際のサイズ変更に関連付けられたコードである。

public static Bitmap ResizeBitmap( Bitmap originalBitmap, int requiredHeight, int requiredWidth )
{
   int[] heightWidthRequiredDimensions;

   // Pass dimensions to worker method depending on image type required
   heightWidthRequiredDimensions = WorkDimensions(originalBitmap.Height, originalBitmap.Width, requiredHeight, requiredWidth);


   Bitmap resizedBitmap = new Bitmap( heightWidthRequiredDimensions[1],
                                      heightWidthRequiredDimensions[0] );

   const float resolution = 72;

   resizedBitmap.SetResolution( resolution, resolution );

   Graphics graphic = Graphics.FromImage( (Image) resizedBitmap );

   graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
   graphic.DrawImage( originalBitmap, 0, 0, resizedBitmap.Width, resizedBitmap.Height );

   graphic.Dispose();
   originalBitmap.Dispose();
   //resizedBitmap.Dispose(); // Still in use


   return resizedBitmap;
}


private static int[] WorkDimensions(int originalHeight, int originalWidth, int requiredHeight, int requiredWidth )
{
   int imgHeight = 0;
   int imgWidth = 0;

   imgWidth = requiredHeight;
   imgHeight = requiredWidth;


   int requiredHeightLocal = originalHeight;
   int requiredWidthLocal = originalWidth;

   double ratio = 0;

   // Check height first
   // If original height exceeds maximum, get new height and work ratio.
   if ( originalHeight > imgHeight )
   {
       ratio = double.Parse( ( (double) imgHeight / (double) originalHeight ).ToString() );
       requiredHeightLocal = imgHeight;
       requiredWidthLocal = (int) ( (decimal) originalWidth * (decimal) ratio );
   }

   // Check width second. It will most likely have been sized down enough
   // in the previous if statement. If not, change both dimensions here by width.
   // If new width exceeds maximum, get new width and height ratio.
   if ( requiredWidthLocal >= imgWidth )
   {
       ratio = double.Parse( ( (double) imgWidth / (double) originalWidth ).ToString() );
       requiredWidthLocal = imgWidth;
       requiredHeightLocal = (int) ( (double) originalHeight * (double) ratio );
   }

   int[] heightWidthDimensionArr = { requiredHeightLocal, requiredWidthLocal };

   return heightWidthDimensionArr;
}
}

（必要な場合）このブログ記事は、完全なソース画像のサイズ変更のためのコード、および圧縮が含まれている

ます。http：//ブログ.bombdefused.com / 2010/08 /バルク画像オプティマイザ・イン・C-フルsource.html の

私は正常に画像のビットマップを作成し、ビットマップのサイズを変更することでこれをやった...これがこれを行うための最善あるいは最も効率的な方法ですが、それは私のために働くかどうかはわかりません。

私の場合、私は半分で、画像の高さと幅をカットする必要がありました。

ここに私がやったことだ。

   private Image getImageFromBytes(byte[] myByteArray)
    {                        
        System.IO.MemoryStream newImageStream = new System.IO.MemoryStream(myByteArray, 0, myByteArray.Length);
        Image image = Image.FromStream(newImageStream, true);
        Bitmap resized = new Bitmap(image, image.Width / 2, image.Height / 2);
        image.Dispose();
        newImageStream.Dispose();
        return resized;
    }

public static System.Drawing.Image ScaleImage(System.Drawing.Image image, int maxImageHeight)
    {
        /* we will resize image based on the height/width ratio by passing expected height as parameter. Based on Expected height and current image height, new ratio will be arrived and using the same we will do the resizing of image width. */

        var ratio = (double)maxImageHeight / image.Height;
        var newWidth = (int)(image.Width * ratio);
        var newHeight = (int)(image.Height * ratio);
        var newImage = new Bitmap(newWidth, newHeight);
        using (var g = Graphics.FromImage(newImage))
        {
            g.DrawImage(image, 0, 0, newWidth, newHeight);
        }
        return newImage;
    }

  decimal size = Math.Round(((decimal)fUpload.PostedFile.ContentLength / (decimal)1024), 2);
        DirectoryInfo dir = new DirectoryInfo(MapPath("Images"));
        FileInfo[] files = dir.GetFiles();
         foreach (FileInfo info in files)
        {
              decimal size2 = Math.Round(((decimal)info.Length / (decimal)1024), 2);
              string Image_name = info.Name.ToString();
              string targetPath = Server.MapPath("Images/" + Image_name);
              string strm = Server.MapPath("Images/" + Image_name);
              var targetFile = targetPath;
              ReduceImageSize(0.5, strm, targetFile, Image_name);
         }

   // Fixed Size Image Generate Code
 protected void btnUpload_Click(object sender, EventArgs e)
    {

 decimal size = Math.Round(((decimal)fUpload.PostedFile.ContentLength / (decimal)1024), 2);
        DirectoryInfo dir = new DirectoryInfo(MapPath("Images"));
        FileInfo[] files = dir.GetFiles();
         foreach (FileInfo info in files)
        {
              decimal size2 = Math.Round(((decimal)info.Length / (decimal)1024), 2);
              string Image_name = info.Name.ToString();
              string targetPath = Server.MapPath("Images/" + Image_name);
              string strm = Server.MapPath("Images/" + Image_name);
              var targetFile = targetPath;
              ReduceImageSize(0.5, strm, targetFile, Image_name);
         }
}

 public void ReduceImageSize(double scaleFactor, String sourcePath, string targetPath, string Image_name)
    {

 // Fixed Size Image Generate Code

       public void ReduceImageSize(double scaleFactor, String sourcePath, string targetPath, string Image_name)
    {
        using (var image = System.Drawing.Image.FromFile(sourcePath))
               {

            //var newWidth = (int)(image.Width  * scaleFactor);
            //var newHeight = (int)(image.Height * scaleFactor);
            var newWidth = (int)(500 * scaleFactor);
            var newHeight = (int)(500 * scaleFactor);
            var thumbnailImg = new Bitmap(newWidth, newHeight);
            var thumbGraph = Graphics.FromImage(thumbnailImg);
            thumbGraph.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
            thumbGraph.SmoothingMode = SmoothingMode.HighQuality;
            thumbGraph.InterpolationMode = InterpolationMode.HighQualityBicubic;
            var imageRectangle = new System.Drawing.RectangleF (0, 0, newWidth, newHeight);
            thumbGraph.DrawImage(image, imageRectangle);


            MemoryStream s = new MemoryStream();
            thumbnailImg.Save(s, System.Drawing.Imaging.ImageFormat.Png);
            s.Position = 0;
            byte[] image2 = new byte[525000];// 512kb =525000  
            s.Read(image2, 0, image2.Length);

            Guid guid = Guid.NewGuid();
            string Server_MapPath = Server.MapPath("~/Image Compress/" + Image_name + guid.ToString() + ".PNG");//Your Compressor Image Save Path

            System.IO.FileStream fs = new System.IO.FileStream(Server_MapPath, System.IO.FileMode.Create, System.IO.FileAccess.ReadWrite);
            fs.Write(image2, 0, image2.Length);

        }
    }
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