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我將圖像字節數組保存爲縮略圖。問題是透明背景顏色在我的圖像中是黑色的。爲什麼透明像素在圖像中顯示爲黑色？
下面是我的代碼：
MemoryStream memoryStream = new MemoryStream(pbytImageByteArray);
System.Drawing.Image imgImageSource = System.Drawing.Image.FromStream(memoryStream);
double dblOrgnWidth = imgImageSource.Width;
double dblOrgnHeight = imgImageSource.Height;
double dblRatio = (dblOrgnWidth/dblOrgnHeight) * 100;
double dblScaledWidth = pintWidth;
double dblScaledHeight = 0;
dblScaledHeight = (dblScaledWidth/dblRatio) * 100;
System.Drawing.Bitmap bitmapImage = new System.Drawing.Bitmap(System.Convert.ToInt32(dblScaledWidth), System.Convert.ToInt32(dblScaledHeight));
bitmapImage.SetResolution(imgImageSource.HorizontalResolution, imgImageSource.VerticalResolution);
System.Drawing.Graphics graphics = System.Drawing.Graphics.FromImage(bitmapImage);
graphics.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceOver;
graphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
ImageAttributes imageAttributes = new ImageAttributes();
graphics.DrawImage(imgImageSource, new System.Drawing.Rectangle(0, 0, System.Convert.ToInt32(dblScaledWidth), System.Convert.ToInt32(dblScaledHeight)), 0, 0, System.Convert.ToInt32(dblOrgnWidth), System.Convert.ToInt32(dblOrgnHeight), System.Drawing.GraphicsUnit.Pixel);
MemoryStream outputMemoryStream = new MemoryStream();
bitmapImage.Save(outputMemoryStream, System.Drawing.Imaging.ImageFormat.Jpeg);
bitmapImage.GetThumbnailImage(System.Convert.ToInt32(dblScaledWidth), System.Convert.ToInt32(dblScaledHeight), null, IntPtr.Zero);
imgImageSource.Dispose();
bitmapImage.Dispose();
graphics.Dispose();
return outputMemoryStream.ToArray();