Crear imagen en miniatura

Quiero mostrar una imagen en miniatura en una vista de cuadrícula desde la ubicación del archivo. ¿Cómo generar eso del archivo .jpeg ? Estoy usando C# lenguaje C# con asp.net .

Tienes que usar el método GetThumbnailImage en la clase de Image :

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

Aquí hay un ejemplo aproximado que toma un archivo de imagen y crea una imagen en miniatura de él, luego lo guarda de nuevo en el disco.

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

El siguiente código escribirá una imagen proporcional a la respuesta, puede modificar el código para su propósito:

 public void WriteImage(string 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(); } 

Aquí hay un ejemplo completo de cómo crear una imagen más pequeña (miniatura). Este fragmento cambia el tamaño de la imagen, la gira cuando sea necesario (si el teléfono se sostuvo verticalmente) y almohadilla la imagen si desea crear pulgares cuadrados. Este fragmento crea un JPEG, pero puede modificarse fácilmente para otros tipos de archivos. Incluso si la imagen fuera más pequeña que el tamaño máximo permitido, la imagen se comprimirá y su resolución se alterará para crear imágenes del mismo nivel de ppp y compresión.

 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(string 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); } } 

Para los usuarios de asp.net, un pequeño ejemplo de cómo cargar un archivo, cambiar su tamaño y mostrar el resultado en la página.

 //== 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; } } }

Aquí hay un ejemplo para convertir imágenes de alta resolución en tamaño de miniatura:

 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; } 

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