C＃GDI +圖片縮放功能

Question

所以我的邏輯是有缺陷的，我需要一個更好的和正確的方式在我的C＃應用​​程序來調整圖像

我需要類似於此設置函數

public void ResizeImageForWeb(string OriginalFile, string NewFile, int MaxWidth, int MaxHeight, int Quality) 
{ 
// Resize Code 

} 

基本上，我是一名網頁設計師，無法嘗試編寫桌面應用程序。

Answer 1

從Google快速搜索找到這個小snippet。

Answer 2

這是我用來調整圖像大小的代碼，用戶上傳的圖像可能會創建縮略圖或者只是爲了強制執行大小限制。它不涉及圖像質量，但它是一個開始。

// uses System.Drawing namespace 
public class ImageResizer 
{ 
    public bool ResizeImage(string fullFileName, int maxHeight, int maxWidth) 
    { 
     return this.ResizeImage(fullFileName, maxHeight, maxWidth, fullFileName); 
    } 

    public bool ResizeImage(string fullFileName, int maxHeight, int maxWidth, string newFileName) 
    { 
     using (Image originalImage = Image.FromFile(fullFileName)) 
     { 
      int height = originalImage.Height; 
      int width = originalImage.Width; 
      int newHeight = maxHeight; 
      int newWidth = maxWidth; 

      if (height > maxHeight || width > maxWidth) 
      { 
       if (height > maxHeight) 
       { 
        newHeight = maxHeight; 
        float temp = ((float)width/(float)height) * (float)maxHeight; 
        newWidth = Convert.ToInt32(temp); 

        height = newHeight; 
        width = newWidth; 
       } 

       if (width > maxWidth) 
       { 
        newWidth = maxWidth; 
        float temp = ((float)height/(float)width) * (float)maxWidth; 
        newHeight = Convert.ToInt32(temp); 
       } 

       Image.GetThumbnailImageAbort abort = new Image.GetThumbnailImageAbort(ThumbnailCallback); 
       using (Image resizedImage = originalImage.GetThumbnailImage(newWidth, newHeight, abort, System.IntPtr.Zero)) 
       { 
        resizedImage.Save(newFileName); 
       } 

       return true; 
      } 
      else if (fullFileName != newFileName) 
      { 
       // no resizing necessary, but need to create new file 
       originalImage.Save(newFileName); 
      } 
     } 

     return false; 
    } 

    private bool ThumbnailCallback() 
    { 
     return false; 
    } 
} 

Answer 3

使用Graphics.DrawImage（）。 GetThumbnailImage（）將從jpeg文件返回一個120x120（或更小）的嵌入縮略圖。對於超過這個尺寸的任何東西將是可怕的。

請參閱http://nathanaeljones.com/163/20-image-resizing-pitfalls/以瞭解適用的設置。

Answer 4

我肯定不會使用GetThumbnailImage，因爲它會令人震驚 - 對於不使用DX或OpenL等的良好分辨率，我會使用類似下面的內容（從我自己的圖形庫中，我用在許多Windows應用程序 - 我有之前共享過幾次，所以可能會有變體浮在網上）。這裏有3個方法 - GetNonIndexedPixelFormat方法用於在傳遞的像素格式無法處理時阻止GDI崩潰（註釋解釋它）。第一個允許縮放一個因子（縮放），最後一個允許固定尺寸縮放，同時保持縱橫比（但如果您想改變它的話，可以很容易地修改）。享受：

/// <summary> 
    /// Scale Image By A Percentage - Scale Factor between 0 and 1. 
    /// </summary> 
    /// <param name="originalImg">Image: Image to scale</param> 
    /// <param name="ZoomFactor">Float: Sclae Value - 0 to 1 are the usual values</param> 
    /// <returns>Image: Scaled Image</returns> 
    public static Image ScaleByPercent(Image originalImg, float ZoomFactor) 
    {  
     int destWidth = (int)((float)originalImg.Width * ZoomFactor); 
     int destHeight = (int)((float)originalImg.Height * ZoomFactor); 

     Bitmap bmPhoto = new Bitmap(destWidth, destHeight, GetNonIndexedPixelFormat(originalImg)); // PixelFormat.Format24bppRgb); 

     bmPhoto.SetResolution(originalImg.HorizontalResolution, originalImg.VerticalResolution); 

     Graphics grPhoto = Graphics.FromImage(bmPhoto); 
     grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic; 

     grPhoto.DrawImage(originalImg, 
      new Rectangle(0, 0, destWidth, destHeight), 
      new Rectangle(0, 0, originalImg.Width, originalImg.Height), 
      GraphicsUnit.Pixel); 

     grPhoto.Dispose(); 
     return bmPhoto; 
    } 

    /// <summary> 
    /// Gets the closest non-indexed pixel format 
    /// </summary> 
    /// <param name="originalImage">Image: Original image</param> 
    /// <returns>PixelFormat: Closest non-pixel image format</returns> 
    public static PixelFormat GetNonIndexedPixelFormat(Image originalImage) 
    { 
     /* 
     * These formats cause an error when creating a GDI Graphics Oblect, so must be converted to non Indexed 
     * Error is "A graphics object cannot be created from an image that has an indexed pixel format" 
     * 
      PixelFormat.Undefined 
      PixelFormat.DontCare 
      PixelFormat.1bppIndexed 
      PixelFormat.4bppIndexed 
      PixelFormat.8bppIndexed 
      PixelFormat.16bppGrayScale 
      PixelFormat.16bppARGB1555 
     * 
     * An attempt is made to use the closest (i.e. smallest fitting) format that will hold the palette. 
     */ 

     switch (originalImage.PixelFormat) 
     { 
      case PixelFormat.Undefined: 
       //This is also the same Enumation as PixelFormat.DontCare: 
       return PixelFormat.Format24bppRgb; 
      case PixelFormat.Format1bppIndexed: 
       return PixelFormat.Format16bppRgb555; 
      case PixelFormat.Format4bppIndexed: 
       return PixelFormat.Format16bppRgb555; 
      case PixelFormat.Format8bppIndexed: 
       return PixelFormat.Format16bppRgb555; 
      case PixelFormat.Format16bppGrayScale: 
       return PixelFormat.Format16bppArgb1555; 
      case PixelFormat.Format32bppArgb: 
       return PixelFormat.Format24bppRgb;     
      default: 
       return originalImage.PixelFormat; 
     } 
    } 

    /// <summary> 
    /// Resize image keeping aspect ratio. 
    /// </summary> 
    /// <param name="originalImg">Image: Image to scale</param> 
    /// <param name="Width">Int: Required width in pixels</param> 
    /// <param name="Height">Int: Required height in pixels</param> 
    /// <param name="BackgroundColour">Color: Background colour</param> 
    /// <returns>Image: Scaled Image</returns> 
    public static Image Resize(Image originalImg, int Width, int Height, Color BackgroundColour) 
    { 
     int destX = 0; 
     int destY = 0; 

     float nPercent = 0f; 

     float nPercentW = ((float)Width/(float)originalImg.Width); 
     float nPercentH = ((float)Height/(float)originalImg.Height); 

     if (nPercentH < nPercentW) 
     { 
      nPercent = nPercentH; 
      destX = System.Convert.ToInt16(((float)Width - ((float)originalImg.Width * nPercent))/2f); 
     } 
     else 
     { 
      nPercent = nPercentW; 
      destY = System.Convert.ToInt16(((float)Height - ((float)originalImg.Height * nPercent))/2f); 
     } 

     int destWidth = (int)(originalImg.Width * nPercent); 
     int destHeight = (int)(originalImg.Height * nPercent); 

     Bitmap bmPhoto = new Bitmap(Width, Height, GetNonIndexedPixelFormat(originalImg)); // PixelFormat.Format24bppRgb); 

     bmPhoto.SetResolution(originalImg.HorizontalResolution, originalImg.VerticalResolution); 

     Graphics grPhoto = Graphics.FromImage(bmPhoto); 
     grPhoto.Clear(BackgroundColour); 
     grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic; 

     grPhoto.DrawImage(originalImg, 
      new Rectangle(destX, destY, destWidth, destHeight), 
      new Rectangle(0, 0, originalImg.Width, originalImg.Height), GraphicsUnit.Pixel); 

     grPhoto.Dispose(); 
     return bmPhoto; 
    }