縮放圖像，但保持其比例

Question

我想縮放圖像，但我不希望圖像看起來偏斜。

圖像必須是115x115（長x寬）。

圖像不能超過115像素高（長度），但如果需要，寬度可以小於115但不會更多。

這是棘手？

Answer 1

您正在尋找縮放圖像，並保留寬高比：

float MaxRatio = MaxWidth/(float) MaxHeight; 
float ImgRatio = source.Width/(float) source.Height; 

if (source.Width > MaxWidth) 
return new Bitmap(source, new Size(MaxWidth, (int) Math.Round(MaxWidth/
ImgRatio, 0))); 

if (source.Height > MaxHeight) 
return new Bitmap(source, new Size((int) Math.Round(MaxWidth * ImgRatio, 
0), MaxHeight)); 

return source; 

應該幫助你，如果你有興趣的想法：Wikpedia article on Image Aspect Ratio

Answer 2

看看Bertrands blog post關於使用GDI和WPF縮放圖像。

Answer 3

需要保留寬高比：

float scale = 0.0; 

    if (newWidth > maxWidth || newHeight > maxHeight) 
    { 
     if (maxWidth/newWidth < maxHeight/newHeight) 
     { 
      scale = maxWidth/newWidth; 
     } 
     else 
     { 
      scale = maxHeight/newHeight; 
     } 
     newWidth = newWidth*scale; 
     newHeight = newHeight*scale; 

    } 

在代碼中，最初newWidth/newHeight是圖像的寬度/高度。

Answer 4

基於的Brij的答案我做了這個擴展方法：

/// <summary> 
/// Resize image to max dimensions 
/// </summary> 
/// <param name="img">Current Image</param> 
/// <param name="maxWidth">Max width</param> 
/// <param name="maxHeight">Max height</param> 
/// <returns>Scaled image</returns> 
public static Image Scale(this Image img, int maxWidth, int maxHeight) 
{ 
    double scale = 1; 

    if (img.Width > maxWidth || img.Height > maxHeight) 
    { 
     double scaleW, scaleH; 

     scaleW = maxWidth/(double)img.Width; 
     scaleH = maxHeight/(double)img.Height; 

     scale = scaleW < scaleH ? scaleW : scaleH; 
    } 

    return img.Resize((int)(img.Width * scale), (int)(img.Height * scale)); 
} 

/// <summary> 
/// Resize image to max dimensions 
/// </summary> 
/// <param name="img">Current Image</param> 
/// <param name="maxDimensions">Max image size</param> 
/// <returns>Scaled image</returns> 
public static Image Scale(this Image img, Size maxDimensions) 
{ 
    return img.Scale(maxDimensions.Width, maxDimensions.Height); 
} 

容量調整方法：

/// <summary> 
/// Resize the image to the given Size 
/// </summary> 
/// <param name="img">Current Image</param> 
/// <param name="width">Width size</param> 
/// <param name="height">Height size</param> 
/// <returns>Resized Image</returns> 
public static Image Resize(this Image img, int width, int height) 
{ 
    return img.GetThumbnailImage(width, height, null, IntPtr.Zero); 
}