Créer une image miniature

Je souhaite afficher une image miniature dans un quadrillage à partir de l’emplacement du fichier. Comment générer celui du fichier .jpeg ? J’utilise le langage C# avec asp.net .

    Vous devez utiliser la méthode GetThumbnailImage dans la classe Image :

    https://msdn.microsoft.com/en-us/library/8t23aykb%28v=vs.110%29.aspx

    Voici un exemple approximatif qui prend un fichier image et en fait une image miniature, puis l’enregistre sur le disque.

     Image image = Image.FromFile(fileName); Image thumb = image.GetThumbnailImage(120, 120, ()=>false, IntPtr.Zero); thumb.Save(Path.ChangeExtension(fileName, "thumb")); 

    Le code suivant écrira une image au prorata de la réponse, vous pouvez modifier le code pour votre objective:

     public void WriteImage(ssortingng path, int width, int height) { Bitmap srcBmp = new Bitmap(path); float ratio = srcBmp.Width / srcBmp.Height; SizeF newSize = new SizeF(width, height * ratio); Bitmap target = new Bitmap((int) newSize.Width,(int) newSize.Height); HttpContext.Response.Clear(); HttpContext.Response.ContentType = "image/jpeg"; using (Graphics graphics = Graphics.FromImage(target)) { graphics.CompositingQuality = CompositingQuality.HighSpeed; graphics.InterpolationMode = InterpolationMode.HighQualityBicubic; graphics.CompositingMode = CompositingMode.SourceCopy; graphics.DrawImage(srcBmp, 0, 0, newSize.Width, newSize.Height); using (MemoryStream memoryStream = new MemoryStream()) { target.Save(memoryStream, ImageFormat.Jpeg); memoryStream.WriteTo(HttpContext.Response.OutputStream); } } Response.End(); } 

    Voici un exemple complet de création d’une image plus petite (vignette). Cet extrait redimensionne l’image, la fait pivoter au besoin (si un téléphone est tenu verticalement) et remplit l’image si vous souhaitez créer des pouces carrés. Cet extrait crée un fichier JPEG, mais il peut facilement être modifié pour d’autres types de fichiers. Même si l’image est inférieure à la taille maximale autorisée, l’image sera toujours compressée et sa résolution sera modifiée pour créer des images de même résolution et niveau de compression.

     using System; using System.Drawing; using System.Drawing.Drawing2D; using System.Drawing.Imaging; using System.IO; //set the resolution, 72 is usually good enough for displaying images on monitors float imageResolution = 72; //set the compression level. higher compression = better quality = bigger images long compressionLevel = 80L; public Image resizeImage(Image image, int maxWidth, int maxHeight, bool padImage) { int newWidth; int newHeight; //first we check if the image needs rotating (eg phone held vertical when taking a picture for example) foreach (var prop in image.PropertyItems) { if (prop.Id == 0x0112) { int orientationValue = image.GetPropertyItem(prop.Id).Value[0]; RotateFlipType rotateFlipType = getRotateFlipType(orientationValue); image.RotateFlip(rotateFlipType); break; } } //apply the padding to make a square image if (padImage == true) { image = applyPaddingToImage(image, Color.Red); } //check if the with or height of the image exceeds the maximum specified, if so calculate the new dimensions if (image.Width > maxWidth || image.Height > maxHeight) { double ratioX = (double)maxWidth / image.Width; double ratioY = (double)maxHeight / image.Height; double ratio = Math.Min(ratioX, ratioY); newWidth = (int)(image.Width * ratio); newHeight = (int)(image.Height * ratio); } else { newWidth = image.Width; newHeight = image.Height; } //start the resize with a new image Bitmap newImage = new Bitmap(newWidth, newHeight); //set the new resolution newImage.SetResolution(imageResolution, imageResolution); //start the resizing using (var graphics = Graphics.FromImage(newImage)) { //set some encoding specs graphics.CompositingMode = CompositingMode.SourceCopy; graphics.CompositingQuality = CompositingQuality.HighQuality; graphics.SmoothingMode = SmoothingMode.HighQuality; graphics.InterpolationMode = InterpolationMode.HighQualityBicubic; graphics.PixelOffsetMode = PixelOffsetMode.HighQuality; graphics.DrawImage(image, 0, 0, newWidth, newHeight); } //save the image to a memorystream to apply the compression level using (MemoryStream ms = new MemoryStream()) { EncoderParameters encoderParameters = new EncoderParameters(1); encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality, compressionLevel); newImage.Save(ms, getEncoderInfo("image/jpeg"), encoderParameters); //save the image as byte array here if you want the return type to be a Byte Array instead of Image //byte[] imageAsByteArray = ms.ToArray(); } //return the image return newImage; } //=== image padding public Image applyPaddingToImage(Image image, Color backColor) { //get the maximum size of the image dimensions int maxSize = Math.Max(image.Height, image.Width); Size squareSize = new Size(maxSize, maxSize); //create a new square image Bitmap squareImage = new Bitmap(squareSize.Width, squareSize.Height); using (Graphics graphics = Graphics.FromImage(squareImage)) { //fill the new square with a color graphics.FillRectangle(new SolidBrush(backColor), 0, 0, squareSize.Width, squareSize.Height); //put the original image on top of the new square graphics.DrawImage(image, (squareSize.Width / 2) - (image.Width / 2), (squareSize.Height / 2) - (image.Height / 2), image.Width, image.Height); } //return the image return squareImage; } //=== get encoder info private ImageCodecInfo getEncoderInfo(ssortingng mimeType) { ImageCodecInfo[] encoders = ImageCodecInfo.GetImageEncoders(); for (int j = 0; j < encoders.Length; ++j) { if (encoders[j].MimeType.ToLower() == mimeType.ToLower()) { return encoders[j]; } } return null; } //=== determine image rotation private RotateFlipType getRotateFlipType(int rotateValue) { RotateFlipType flipType = RotateFlipType.RotateNoneFlipNone; switch (rotateValue) { case 1: flipType = RotateFlipType.RotateNoneFlipNone; break; case 2: flipType = RotateFlipType.RotateNoneFlipX; break; case 3: flipType = RotateFlipType.Rotate180FlipNone; break; case 4: flipType = RotateFlipType.Rotate180FlipX; break; case 5: flipType = RotateFlipType.Rotate90FlipX; break; case 6: flipType = RotateFlipType.Rotate90FlipNone; break; case 7: flipType = RotateFlipType.Rotate270FlipX; break; case 8: flipType = RotateFlipType.Rotate270FlipNone; break; default: flipType = RotateFlipType.RotateNoneFlipNone; break; } return flipType; } //== convert image to base64 public string convertImageToBase64(Image image) { using (MemoryStream ms = new MemoryStream()) { //convert the image to byte array image.Save(ms, ImageFormat.Jpeg); byte[] bin = ms.ToArray(); //convert byte array to base64 string return Convert.ToBase64String(bin); } } 

    Pour les utilisateurs d'asp.net, un petit exemple de la façon de télécharger un fichier, de le redimensionner et d'afficher le résultat sur la page.

     //== the button click method protected void Button1_Click(object sender, EventArgs e) { //check if there is an actual file being uploaded if (FileUpload1.HasFile == false) { return; } using (Bitmap bitmap = new Bitmap(FileUpload1.PostedFile.InputStream)) { try { //start the resize Image image = resizeImage(bitmap, 256, 256, true); //to visualize the result, display as base64 image Label1.Text = ""; //save your image to file sytem, database etc here } catch (Exception ex) { Label1.Text = "Oops! There was an error when resizing the Image.
    Error: " + ex.Message; } } }

    Voici un exemple pour convertir une image haute résolution en taille de vignette-

     protected void Button1_Click(object sender, EventArgs e) { //---------- Getting the Image File System.Drawing.Image img = System.Drawing.Image.FromFile(Server.MapPath("~/profile/Avatar.jpg")); //---------- Getting Size of Original Image double imgHeight = img.Size.Height; double imgWidth = img.Size.Width; //---------- Getting Decreased Size double x = imgWidth / 200; int newWidth = Convert.ToInt32(imgWidth / x); int newHeight = Convert.ToInt32(imgHeight / x); //---------- Creating Small Image System.Drawing.Image.GetThumbnailImageAbort myCallback = new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback); System.Drawing.Image myThumbnail = img.GetThumbnailImage(newWidth, newHeight, myCallback, IntPtr.Zero); //---------- Saving Image myThumbnail.Save(Server.MapPath("~/profile/NewImage.jpg")); } public bool ThumbnailCallback() { return false; } 

    Source- http://iknowledgeboy.blogspot.in/2014/03/c-creating-thumbnail-of-large-image-by.html