Question

我将图像字节数组保存为缩略图。问题是我的图像中透明背景颜色是黑色。

以下是我的代码：

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();

Answer 1

JPEG不支持透明度。保存为PNG。

或者，如果您知道将使用的背景颜色，则可以将透明像素设置为该颜色。如果您使用半透明像素，则必须将像素与该颜色混合。

这是一篇解释alpha混合的文章：

http://www.c-sharpcorner.com/UploadFile/mahesh/DrawTransparentImageUsingAB10102005010514AM/DrawTransparentImageUsingAB.aspx

如果您对商业解决方案感兴趣（免责声明：我为Atalasoft工作），DotImage Photo有一个类FlattenAlphaCommand，可以用几行代码来完成。< / p>

为什么透明像素在我的图像中显示为黑色？

1 个答案: