C# 影像縮圖

出處

/// <summary>自動縮圖</summary>

/// <param name="img">檔案本體</param>

/// <param name="filePath">存放位置</param>

/// <param name="fileName">檔案名稱</param>

protected void reDrawingImg(byte[] imgBuffer, string filePath, string fileName) {

System.Drawing.Image img = bufferToImage(imgBuffer);

ImageFormat thisFormat = img.RawFormat;   //取得影像的格式

int[] newWH = imgReSize(img.Width, img.Height);

Bitmap imageOutput = new Bitmap(img, newWH[0], newWH[1]);

        //縮圖後存放指定位址

imageOutput.Save(filePath + fileName, thisFormat);

imageOutput.Dispose();   //釋放記憶體

img.Dispose();               //釋放掉圖檔

}

/// <summary>將 byte[] 轉成 Image</summary>

/// <param name="Buffer">檔案本體 (byte[])</param>

private System.Drawing.Image bufferToImage(byte[] Buffer) {

byte[] data = null;

System.Drawing.Image oImage = null;

MemoryStream oMemoryStream = null;

Bitmap oBitmap = null;

//建立副本

data = (byte[])Buffer.Clone();

try {

oMemoryStream = new MemoryStream(data);

//設定資料流位置

oMemoryStream.Position = 0;

oImage = System.Drawing.Image.FromStream(oMemoryStream);

//建立副本

oBitmap = new Bitmap(oImage);                

} catch {

throw;

}

finally {

oMemoryStream.Close();

oMemoryStream.Dispose();

oMemoryStream = null;

}

return oBitmap;

}

/// <summary>等比縮圖 - 計算長寬</summary>

/// <param name="width">原始寬度</param>

/// <param name="height">原始高度</param>

protected int[] imgReSize(double width, double height) {

int[] newWH = new int[2];

double rate, rWidth, rHeight;

if (width > height && width > 200) {

//水平圖

rWidth = 200;

rate = rWidth / width;

rHeight = height * rate;

newWH[0] = (int)rWidth;

newWH[1] = (int)rHeight;

}

else if (height > width && height > 150) {

//垂直圖

rHeight = 150;

rate = rHeight / height;

rWidth = width * rate;

newWH[0] = (int)rWidth;

newWH[1] = (int)rHeight;

}

else {

newWH[0] = (int)width;

newWH[1] = (int)height;

}

return newWH;

}