c# - ディスクに保存せずに画像のサイズを変更する

Question

asp.netで、画像のサイズを変更して、ディスクに保存せずに、いくつかのコントロールに表示したいと思います。古典的なaspのような無料のユーティリティはありますか？

http://www.aspjpeg.com/livedemo.html

Answer 1

このサムネイルクラスがその役割を果たします。

public class Thumbnail
{
    private string _filePath;
    private int _maxWidth = 120;
    private int _maxHeight = 120;

    public string MimeType;
    public System.Drawing.Imaging.ImageFormat ImageFormat;
    public byte[] ImageBytes;

    public Thumbnail(string filePath, int maxWidth, int maxHeight)
    {
        _filePath = filePath;
        _maxWidth = maxWidth;
        _maxHeight = maxHeight;

        MakeThumbnail();
    }

    private void MakeThumbnail()
    {
        using (Image img = new Bitmap(_filePath))
        {
            Size newSize = GenerateImageDimensions(img.Width, img.Height, _maxWidth, _maxHeight);
            int imgWidth = newSize.Width;
            int imgHeight = newSize.Height;

            // create the thumbnail image
            using (Image img2 =
                      img.GetThumbnailImage(imgWidth, imgHeight,
                      new Image.GetThumbnailImageAbort(Abort),
                      IntPtr.Zero))
            {

                using (Graphics g = Graphics.FromImage(img2)) // Create Graphics object from original Image
                {
                    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                    g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
                    g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;

                    //BMP 0, JPEG 1 , GIF 2 , TIFF 3, PNG 4
                    System.Drawing.Imaging.ImageCodecInfo codec;

                    switch (Path.GetExtension(_filePath))
                    {
                        case ".gif":
                            codec = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders()[2];
                            ImageFormat = System.Drawing.Imaging.ImageFormat.Gif;
                            MimeType = "image/gif";
                            break;

                        case ".png":
                            codec = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders()[4];
                            ImageFormat = System.Drawing.Imaging.ImageFormat.Png;
                            MimeType = "image/png";
                            break;

                        default: //jpg
                            codec = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders()[1];
                            ImageFormat = System.Drawing.Imaging.ImageFormat.Jpeg;
                            MimeType = "image/jpg";
                            break;
                    }

                    //Set the parameters for defining the quality of the thumbnail... here it is set to 100%
                    System.Drawing.Imaging.EncoderParameters eParams = new System.Drawing.Imaging.EncoderParameters(1);
                    eParams.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 90L);

                    //Now draw the image on the instance of thumbnail Bitmap object
                    g.DrawImage(img, new Rectangle(0, 0, img2.Width, img2.Height));

                    MemoryStream ms = new MemoryStream();
                    img2.Save(ms, codec, eParams);
                    ImageBytes = new byte[ms.Length];
                    ImageBytes = ms.ToArray();

                    ms.Close();
                    ms.Dispose();
                }
            }
        }
    }

    public static Size GenerateImageDimensions(int currW, int currH, int destW, int destH)
    {
        int imgWidth = currW;
        int imgHeight = currH;

        if (imgWidth > destW)
        {
            double rate = (double)imgWidth / (double)destW;
            imgWidth = destW;
            imgHeight = (int)(imgHeight / rate);
        }

        if (imgHeight > destH)
        {
            double rate = (double)imgHeight / (double)destH;
            imgHeight = destH;
            imgWidth = (int)(imgWidth / rate);
        }

        return new Size(imgWidth, imgHeight);
    }

    private bool Abort()
    {
        return false;
    }
}

使い方は簡単です。これをページのコードビハインドに配置するだけです。ブラウザの出力は画像のサイズが変更されます。

Thumbnail thm = new Thumbnail("c:\some_image.jpg", 300, 300);
Response.ContentType = thm.MimeType;
Response.BinaryWrite(thm.ImageBytes);

Answer 2

これはおそらくあなたが必要とするものです：

http://imageresizing.net/