c Image resizing to different size while preserving aspect ratio

Question

I m trying to resize an image while preserving the aspect ratio from the original image so the new image doesn t look squashed   eg      Convert a 150 100 image into a 150 150 image    The extra 50 pixels of the height need to be padded with a white background color    This is the current code I am using    It works well for resizing but changing the aspect ratio of the original image squashes the new image   private void resizeImage string path  string originalFilename                            int width  int height                Image image   Image FromFile path   originalFilename            System Drawing Image thumbnail   new Bitmap width  height           System Drawing Graphics graphic                         System Drawing Graphics FromImage thumbnail            graphic InterpolationMode   InterpolationMode HighQualityBicubic          graphic SmoothingMode   SmoothingMode HighQuality          graphic PixelOffsetMode   PixelOffsetMode HighQuality          graphic CompositingQuality   CompositingQuality HighQuality           graphic DrawImage image  0  0  width  height            System Drawing Imaging ImageCodecInfo   info                            ImageCodecInfo GetImageEncoders            EncoderParameters encoderParameters          encoderParameters   new EncoderParameters 1           encoderParameters Param 0    new EncoderParameter Encoder Quality                           100L                       thumbnail Save path   width         originalFilename  info 1                             encoderParameters           EDIT  I d like to have the image padded instead of cropped

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To get a faster result  the function that obtains the size could be found in resultSize   Size original   new Size 640  480    int maxSize   100   float percent    new List lt float gt     float maxSize    float original Width    float maxSize     float original Height    Min     Size resultSize   new Size  int Math Floor original Width   percent    int Math Floor original Height   percent      Uses Linq to minimize variable and recalculations  as well as unnecesary if else statements

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Maintain aspect Ration and eliminate letterbox and Pillarbox   static Image FixedSize Image imgPhoto  int Width  int Height                int sourceWidth   imgPhoto Width          int sourceHeight   imgPhoto Height          int X   0          int Y   0           float nPercent   0          float nPercentW   0          float nPercentH   0           nPercentW     float Width    float sourceWidth           nPercentH     float Height    float sourceHeight           if  nPercentH  lt  nPercentW                        nPercent   nPercentH                    else                       nPercent   nPercentW                     int destWidth    int  sourceWidth   nPercent           int destHeight    int  sourceHeight   nPercent            Bitmap bmPhoto   new Bitmap destWidth  destHeight  PixelFormat Format24bppRgb            bmPhoto SetResolution imgPhoto HorizontalResolution                                           imgPhoto VerticalResolution            Graphics grPhoto   Graphics FromImage bmPhoto            grPhoto DrawImage imgPhoto                  new Rectangle X  Y  destWidth  destHeight                   new Rectangle X  Y  sourceWidth  sourceHeight                   GraphicsUnit Pixel            grPhoto Dispose            return bmPhoto

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I m going to add my code here too  This code will allow you resize an image with or without the aspect ratio being enforced or to resize with padding  This is a modified version of egrunin s code   using System Drawing  using System Drawing Drawing2D  using System Drawing Imaging  using System IO   namespace ConsoleApplication1       public class Program               public static void Main string   args                        var path   Directory GetParent Directory GetCurrentDirectory    Parent FullName              ResizeImage path   large jpg   path   new jpg   100  100  true  true                           lt summary gt Resizes an image to a new width and height  lt  summary gt               lt param name  originalPath  gt The folder which holds the original image  lt  param gt               lt param name  originalFileName  gt The file name of the original image  lt  param gt               lt param name  newPath  gt The folder which will hold the resized image  lt  param gt               lt param name  newFileName  gt The file name of the resized image  lt  param gt               lt param name  maximumWidth  gt When resizing the image  this is the maximum width to resize the image to  lt  param gt               lt param name  maximumHeight  gt When resizing the image  this is the maximum height to resize the image to  lt  param gt               lt param name  enforceRatio  gt Indicates whether to keep the width height ratio aspect or not  If set to false  images with an unequal width and height will be distorted and padding is disregarded  If set to true  the width height ratio aspect is maintained and distortion does not occur  lt  param gt               lt param name  addPadding  gt Indicates whether fill the smaller dimension of the image with a white background  If set to true  the white padding fills the smaller dimension until it reach the specified max width or height  This is used for maintaining a 1 1 ratio if the max width and height are the same  lt  param gt          private static void ResizeImage string originalPath  string originalFileName  string newPath  string newFileName  int maximumWidth  int maximumHeight  bool enforceRatio  bool addPadding                        var image   Image FromFile originalPath          originalFileName               var imageEncoders   ImageCodecInfo GetImageEncoders                EncoderParameters encoderParameters   new EncoderParameters 1               encoderParameters Param 0    new EncoderParameter Encoder Quality  100L               var canvasWidth   maximumWidth              var canvasHeight   maximumHeight              var newImageWidth   maximumWidth              var newImageHeight   maximumHeight              var xPosition   0              var yPosition   0                if  enforceRatio                                var ratioX   maximumWidth    double image Width                  var ratioY   maximumHeight    double image Height                  var ratio   ratioX  lt  ratioY   ratioX   ratioY                  newImageHeight    int  image Height   ratio                   newImageWidth    int  image Width   ratio                    if  addPadding                                        xPosition    int   maximumWidth -  image Width   ratio     2                       yPosition    int   maximumHeight -  image Height   ratio     2                                     else                                       canvasWidth   newImageWidth                      canvasHeight   newImageHeight                                                                 var thumbnail   new Bitmap canvasWidth  canvasHeight               var graphic   Graphics FromImage thumbnail                if  enforceRatio  amp  amp  addPadding                                graphic Clear Color White                              graphic InterpolationMode   InterpolationMode HighQualityBicubic              graphic SmoothingMode   SmoothingMode HighQuality              graphic PixelOffsetMode   PixelOffsetMode HighQuality              graphic CompositingQuality   CompositingQuality HighQuality              graphic DrawImage image  xPosition  yPosition  newImageWidth  newImageHeight                thumbnail Save newPath          newFileName  imageEncoders 1   encoderParameters

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I created a extension method that is much simpiler than the answers that are posted  and the aspect ratio is applied without cropping the image  public static Image Resize this Image image  int width  int height         var scale   Math Min height    float image Height  width    float image Width        return image GetThumbnailImage  int  image Width   scale    int  image Height   scale        gt  false  IntPtr Zero      Example usage  using  var img   Image FromFile pathToOriginalImage         using  var thumbnail   img Resize 60  60               Here you can do whatever you need to do with thumnail

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Note  this code resizes and removes everything outside the aspect ratio instead of padding it    using System  using System Collections Generic  using System Linq  using System Text  using System Drawing  using System Drawing Imaging  using System IO   namespace MyPhotos Common       public class ThumbCreator                public enum VerticalAlign                       Top              Middle              Bottom                    public enum HorizontalAlign                       Left              Middle              Right                    public void Convert string sourceFile  string targetFile  ImageFormat targetFormat  int height  int width  VerticalAlign valign  HorizontalAlign halign                        using  Image img   Image FromFile sourceFile                                 using  Image targetImg   Convert img  height  width  valign  halign                                         string directory   Path GetDirectoryName targetFile                       if   Directory Exists directory                                                 Directory CreateDirectory directory                                             if  targetFormat    ImageFormat Jpeg                                                SaveJpeg targetFile  targetImg  100                                             else                                               targetImg Save targetFile  targetFormat                                                                                 lt summary gt               Saves an image as a jpeg image  with the given quality               lt  summary gt                lt param name  path  gt Path to which the image would be saved  lt  param gt               lt param name  quality  gt An integer from 0 to 100  with 100 being the              highest quality lt  param gt           public static void SaveJpeg string path  Image img  int quality                        if  quality  lt  0    quality  gt  100                  throw new ArgumentOutOfRangeException  quality must be between 0 and 100                      Encoder parameter for image quality              EncoderParameter qualityParam                   new EncoderParameter System Drawing Imaging Encoder Quality  quality                  Jpeg image codec              ImageCodecInfo jpegCodec   GetEncoderInfo  image jpeg                 EncoderParameters encoderParams   new EncoderParameters 1               encoderParams Param 0    qualityParam               img Save path  jpegCodec  encoderParams                           lt summary gt               Returns the image codec with the given mime type               lt  summary gt           private static ImageCodecInfo GetEncoderInfo string mimeType                           Get image codecs for all image formats              ImageCodecInfo   codecs   ImageCodecInfo GetImageEncoders                    Find the correct image codec              for  int i   0  i  lt  codecs Length  i                    if  codecs i  MimeType    mimeType                      return codecs i               return null                     public Image Convert Image img  int height  int width  VerticalAlign valign  HorizontalAlign halign                        Bitmap result   new Bitmap width  height               using  Graphics g   Graphics FromImage result                                 g SmoothingMode   System Drawing Drawing2D SmoothingMode HighQuality                  g InterpolationMode   System Drawing Drawing2D InterpolationMode HighQualityBicubic                  float ratio    float height    float img Height                  int temp    int   float img Width   ratio                   if  temp    width                                          no corrections are needed                      g DrawImage img  0  0  width  height                       return result                                    else if  temp  gt  width                                          den e f  r bred                      int overFlow    temp - width                       if  halign    HorizontalAlign Middle                                                g DrawImage img  0 - overFlow   2  0  temp  height                                             else if  halign    HorizontalAlign Left                                                g DrawImage img  0  0  temp  height                                             else if  halign    HorizontalAlign Right                                                g DrawImage img  -overFlow  0  temp  height                                                           else                                         den e f  r h  g                      ratio    float width    float img Width                      temp    int   float img Height   ratio                       int overFlow    temp - height                       if  valign    VerticalAlign Top                                                g DrawImage img  0  0  width  temp                                             else if  valign    VerticalAlign Middle                                                g DrawImage img  0  -overFlow   2  width  temp                                             else if  valign    VerticalAlign Bottom                                                g DrawImage img  0  -overFlow  width  temp                                                                     return result

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I use the following method to calculate the desired image size   using System Drawing  public static Size ResizeKeepAspect this Size src  int maxWidth  int maxHeight  bool enlarge   false        maxWidth   enlarge   maxWidth   Math Min maxWidth  src Width       maxHeight   enlarge   maxHeight   Math Min maxHeight  src Height        decimal rnd   Math Min maxWidth    decimal src Width  maxHeight    decimal src Height       return new Size  int Math Round src Width   rnd    int Math Round src Height   rnd        This puts the problem of aspect ratio and dimensions in a separate method

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This allows us to resize the image  It prevents skewed images and     also vertically long images caused by trying to maintain the aspect     ratio on images who s height is larger than their width  public void ResizeImage string OriginalFile  string NewFile  int NewWidth  int MaxHeight  bool OnlyResizeIfWider         System Drawing Image FullsizeImage   System Drawing Image FromFile OriginalFile           Prevent using images internal thumbnail     FullsizeImage RotateFlip System Drawing RotateFlipType Rotate180FlipNone       FullsizeImage RotateFlip System Drawing RotateFlipType Rotate180FlipNone        if  OnlyResizeIfWider                if  FullsizeImage Width  lt   NewWidth                        NewWidth   FullsizeImage Width                       int NewHeight   FullsizeImage Height   NewWidth   FullsizeImage Width      if  NewHeight  gt  MaxHeight                   Resize with height instead         NewWidth   FullsizeImage Width   MaxHeight   FullsizeImage Height          NewHeight   MaxHeight             System Drawing Image NewImage   FullsizeImage GetThumbnailImage NewWidth  NewHeight  null  IntPtr Zero           Clear handle to original file so that we can overwrite it if necessary     FullsizeImage Dispose            Save resized picture     NewImage Save NewFile

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public static void resizeImage n save Stream sourcePath  string targetPath  int requiredSize                using  var image   System Drawing Image FromStream sourcePath                         double ratio   0               var newWidth   0              var newHeight   0              double w   Convert ToInt32 image Width               double h   Convert ToInt32 image Height               if  w  gt  h                                ratio   h   w   100                  newWidth   requiredSize                  newHeight   Convert ToInt32 requiredSize   ratio   100                             else                               ratio   w   h   100                  newHeight   requiredSize                  newWidth   Convert ToInt32 requiredSize   ratio   100                                   var newWidth    int  image Width   scaleFactor                  var newHeight    int  image Height   scaleFactor               var thumbnailImg   new Bitmap newWidth  newHeight               var thumbGraph   Graphics FromImage thumbnailImg               thumbGraph CompositingQuality   CompositingQuality HighQuality              thumbGraph SmoothingMode   SmoothingMode HighQuality              thumbGraph InterpolationMode   InterpolationMode HighQualityBicubic              var imageRectangle   new Rectangle 0  0  newWidth  newHeight                thumbGraph DrawImage image  imageRectangle               thumbnailImg Save targetPath  image RawFormat                  var img   FixedSize image  requiredSize  requiredSize                 img Save targetPath  image RawFormat

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I found out how to resize AND pad the image by learning from this this CodeProject Article   static Image FixedSize Image imgPhoto  int Width  int Height                int sourceWidth   imgPhoto Width          int sourceHeight   imgPhoto Height          int sourceX   0          int sourceY   0          int destX   0          int destY   0           float nPercent   0          float nPercentW   0          float nPercentH   0           nPercentW     float Width    float sourceWidth           nPercentH     float Height    float sourceHeight           if  nPercentH  lt  nPercentW                        nPercent   nPercentH              destX   System Convert ToInt16  Width -                            sourceWidth   nPercent     2                     else                       nPercent   nPercentW              destY   System Convert ToInt16  Height -                            sourceHeight   nPercent     2                      int destWidth    int  sourceWidth   nPercent           int destHeight    int  sourceHeight   nPercent            Bitmap bmPhoto   new Bitmap Width  Height                            PixelFormat Format24bppRgb           bmPhoto SetResolution imgPhoto HorizontalResolution                           imgPhoto VerticalResolution            Graphics grPhoto   Graphics FromImage bmPhoto           grPhoto Clear Color Red           grPhoto InterpolationMode                   InterpolationMode HighQualityBicubic           grPhoto DrawImage imgPhoto              new Rectangle destX  destY  destWidth  destHeight               new Rectangle sourceX  sourceY  sourceWidth  sourceHeight               GraphicsUnit Pixel            grPhoto Dispose            return bmPhoto

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This should do it   private void resizeImage string path  string originalFilename                           note changed names                         int canvasWidth  int canvasHeight                           new                         int originalWidth  int originalHeight        Image image   Image FromFile path   originalFilename        System Drawing Image thumbnail            new Bitmap canvasWidth  canvasHeight      changed parm names     System Drawing Graphics graphic                     System Drawing Graphics FromImage thumbnail        graphic InterpolationMode   InterpolationMode HighQualityBicubic      graphic SmoothingMode   SmoothingMode HighQuality      graphic PixelOffsetMode   PixelOffsetMode HighQuality      graphic CompositingQuality   CompositingQuality HighQuality          ------------------ new code ---------------            Figure out the ratio     double ratioX    double  canvasWidth    double  originalWidth      double ratioY    double  canvasHeight    double  originalHeight         use whichever multiplier is smaller     double ratio   ratioX  lt  ratioY   ratioX   ratioY          now we can get the new height and width     int newHeight   Convert ToInt32 originalHeight   ratio       int newWidth   Convert ToInt32 originalWidth   ratio           Now calculate the X Y position of the upper-left corner          one of these will always be zero      int posX   Convert ToInt32  canvasWidth -  originalWidth   ratio     2       int posY   Convert ToInt32  canvasHeight -  originalHeight   ratio     2        graphic Clear Color White      white padding     graphic DrawImage image  posX  posY  newWidth  newHeight           ------------- end new code ----------------         System Drawing Imaging ImageCodecInfo   info                        ImageCodecInfo GetImageEncoders        EncoderParameters encoderParameters      encoderParameters   new EncoderParameters 1       encoderParameters Param 0    new EncoderParameter Encoder Quality                       100L                   thumbnail Save path   newWidth         originalFilename  info 1                         encoderParameters       Edited to add   Those who want to improve this code should put it in the comments  or a new answer  Don t edit this code directly

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Just generalizing it down to aspect ratios and sizes  image stuff can be done outside of this function  public static d RectangleF ScaleRect d RectangleF dest  d RectangleF src     bool keepWidth  bool keepHeight          d RectangleF destRect   new d RectangleF         float sourceAspect   src Width   src Height      float destAspect   dest Width   dest Height       if  sourceAspect  gt  destAspect                   wider than high keep the width and scale the height         destRect Width   dest Width          destRect Height   dest Width   sourceAspect           if  keepHeight                        float resizePerc   dest Height   destRect Height              destRect Width   dest Width   resizePerc              destRect Height   dest Height                      else                  higher than wide     keep the height and scale the width         destRect Height   dest Height          destRect Width   dest Height   sourceAspect           if  keepWidth                        float resizePerc   dest Width   destRect Width              destRect Width   dest Width              destRect Height   dest Height   resizePerc                        return destRect

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I just wrote this cos none of the answers already here were simple enough  You can replace the hardcoded 128 for whatever you want or base them off the size of the original image  All i wanted was to rescale the image into a 128x128 image  keeping the aspect ratio and centering the result in the new image       private Bitmap CreateLargeIconForImage Bitmap src                Bitmap bmp   new Bitmap 128  128           Graphics g   Graphics FromImage bmp            float scale   Math Max  float src Width   128 0f   float src Height   128 0f           PointF p   new PointF 128 0f -   float src Width   scale   128 0f -   float src Height   scale            SizeF size   new SizeF  float src Width   scale   float src Height   scale            g DrawImage src  new RectangleF p  size             return bmp

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Here s a less specific extension method that works with Image rather than doing the loading and saving for you  It also allows you to specify interpolation method and correctly renders edges when you use NearestNeighbour interpolation   The image will be rendered within the bounds of the area you specify so you always know your output width and height  e g     namespace YourApp        region Namespaces     using System      using System Drawing      using System Drawing Imaging      using System Drawing Drawing2D       endregion           lt summary gt Generic helper functions related to graphics  lt  summary gt      public static class ImageExtensions                    lt summary gt Resizes an image to a new width and height value  lt  summary gt               lt param name  image  gt The image to resize  lt  param gt               lt param name  newWidth  gt The width of the new image  lt  param gt               lt param name  newHeight  gt The height of the new image  lt  param gt               lt param name  mode  gt Interpolation mode  lt  param gt               lt param name  maintainAspectRatio  gt If true  the image is centered in the middle of the returned image  maintaining the aspect ratio of the original image  lt  param gt               lt returns gt The new image  The old image is unaffected  lt  returns gt          public static Image ResizeImage this Image image  int newWidth  int newHeight  InterpolationMode mode   InterpolationMode Default  bool maintainAspectRatio   false                        Bitmap output   new Bitmap newWidth  newHeight  image PixelFormat                using  Graphics gfx   Graphics FromImage output                                 gfx Clear Color FromArgb 0  0  0  0                    gfx InterpolationMode   mode                  if  mode    InterpolationMode NearestNeighbor                                        gfx PixelOffsetMode   PixelOffsetMode HighQuality                      gfx SmoothingMode   SmoothingMode HighQuality                                     double ratioW    double newWidth    double image Width                  double ratioH    double newHeight    double image Height                  double ratio   ratioW  lt  ratioH   ratioW   ratioH                  int insideWidth    int  image Width   ratio                   int insideHeight    int  image Height   ratio                    gfx DrawImage image  new Rectangle  newWidth   2  -  insideWidth   2    newHeight   2  -  insideHeight   2   insideWidth  insideHeight                               return output

[c#] c# Image resizing to different size while preserving aspect ratio

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