使用C＃删除图像中的透明度
有没有人知道一个平滑/快速的方法来删除透明度，例如pngs / tiffs等，并用白色背景替换它？
基本上我需要的是我需要创建PDF / A兼容图像，根据规范，它可能具有-no-透明度（因此固定的白色背景很好）。
有什么想法/建议吗？
干杯和谢谢，-Jörg
您可以创建与png大小相同的位图，绘制一个白色矩形，然后在其上绘制图像。
void RemTransp(string file) { Bitmap src = new Bitmap(file); Bitmap target = new Bitmap(src.Size.Width,src.Size.Height); Graphics g = Graphics.FromImage(target); g.DrawRectangle(new Pen(new SolidBrush(Color.White)), 0, 0, target.Width, target.Height); g.DrawImage(src, 0, 0); target.Save("Your target path"); } 您必须删除Alpha通道。 否则你仍然会有一个透明的图像 – 只是没有透明区域。
class Program { static void Main(string[] args) { //this also works for different file formats ReplaceTransparency(@"C:\Y\transparent.png", System.Drawing.Color.White).Save(@"C:\Y\no_transparency.png"); ReplaceTransparency(@"C:\Y\transparent.gif", System.Drawing.Color.White).Save(@"C:\Y\no_transparency.gif"); } public static System.Drawing.Bitmap ReplaceTransparency(string file, System.Drawing.Color background) { return ReplaceTransparency(System.Drawing.Image.FromFile(file), background); } public static System.Drawing.Bitmap ReplaceTransparency(System.Drawing.Image image, System.Drawing.Color background) { return ReplaceTransparency((System.Drawing.Bitmap)image, background); } public static System.Drawing.Bitmap ReplaceTransparency(System.Drawing.Bitmap bitmap, System.Drawing.Color background) { /* Important: you have to set the PixelFormat to remove the alpha channel. * Otherwise you'll still have a transparent image - just without transparent areas */ var result = new System.Drawing.Bitmap(bitmap.Size.Width, bitmap.Size.Height, System.Drawing.Imaging.PixelFormat.Format24bppRgb); var g = System.Drawing.Graphics.FromImage(result); g.Clear(background); g.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceOver; g.DrawImage(bitmap, 0, 0); return result; } }
1）创建一个白色背景和与图像大小相同的位图
2）加载图像并将其绘制在“白色”位图的顶部
3）保存新创建的图像
PNG具有alpha通道，因此简单的重新着色不会。 创建相同大小的白色图像，并创建合成图像覆盖您的图像。
加入Stormenet的答案; 记得用“using”语句包装所有Bitmap和Graphics对象以处理非托管资源。
命名空间：
using Microsoft.Win32; using System.Windows.Media; using System.Windows.Media.Imaging; using PdfSharp; using PdfSharp.Pdf; using PdfSharp.Drawing;
从File创建PNG或TIFF BitmapSource：
BitmapSource BitmapSource; private void OpenFile(Object sender, RoutedEventArgs e) { OpenFileDialog OpenFileDialog = new OpenFileDialog(); OpenFileDialog.Filter = "PNG files (*.png)|*.png|TIFF files (*.tif)|*.tif"; if (OpenFileDialog.ShowDialog() == true) { try { if (OpenFileDialog.OpenFile() != null) { String InitialPath = OpenFileDialog.FileName; FileStream InitialFileStream = new FileStream(InitialPath, FileMode.Open, FileAccess.Read, FileShare.Read); switch (OpenFileDialog.FilterIndex) { case 1: PngBitmapDecoder PngBitmapDecoder = new PngBitmapDecoder(InitialFileStream, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad); BitmapSource = PngBitmapDecoder.Frames[0]; InitialFileStream.Close(); break; case 2: TiffBitmapDecoder TiffBitmapDecoder = new TiffBitmapDecoder(InitialFileStream, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad); BitmapSource = TiffBitmapDecoder.Frames[0]; InitialFileStream.Close(); break; } } } catch (Exception Exception) { MessageBox.Show("Error: Could not read file from disk. Original error: ", Exception.Message, MessageBoxButton.OK, MessageBoxImage.Error); } } }
按钮上的function单击：
private void ButtonClick(Object sender, RoutedEventArgs e) { PixelFormat PixelFormat = BitmapSource.Format; if (PixelFormat == PixelFormats.Bgra32) { try { BitmapSource = Bgra32ToBgra24(BitmapSource); //BitmapSource = Bgra32ToGray8(BitmapSource); } catch (Exception Exception) { MessageBox.Show("Error: Could not convert BitmapSource. Original error: ", Exception.Message, MessageBoxButton.OK, MessageBoxImage.Error); } } }
function：
public static BitmapSource Bgra32ToBgr24(BitmapSource BitmapSource) { Int32 PixelWidth = BitmapSource.PixelWidth; Int32 PixelHeight = BitmapSource.PixelHeight; Double DpiX = BitmapSource.DpiX; Double DpiY = BitmapSource.DpiY; PixelFormat InputPixelFormat = BitmapSource.Format; BitmapPalette InputPalette = BitmapSource.Palette; Int32 InputBitsPerPixel = BitmapSource.Format.BitsPerPixel; Int32 InputStride = PixelWidth * InputBitsPerPixel / 8; Byte[] InputPixelsArray = new Byte[InputStride * PixelHeight]; BitmapSource.CopyPixels(InputPixelsArray, InputStride, 0); PixelFormat PixelFormat = PixelFormats.Bgr24; BitmapPalette Palette = null; Int32 BitsPerPixel = 24; Int32 Stride = PixelWidth * BitsPerPixel / 8; Byte[] PixelsArray = new Byte[InputStride * PixelHeight / 4 * 3]; Int32 i = 0; Int32 j = 0; Int32 k = 0; while (i < InputPixelsArray.Length / 4) { PixelsArray[k] = InputPixelsArray[j]; PixelsArray[k + 1] = InputPixelsArray[j + 1]; PixelsArray[k + 2] = InputPixelsArray[j + 2]; i = i + 1; j = j + 4; k = k + 3; } BitmapSource = BitmapSource.Create(PixelWidth, PixelHeight, DpiX, DpiY, PixelFormat, Palette, PixelsArray, Stride); return BitmapSource; }
将通道转换为Gray8 BitmapSource
public static BitmapSource Bgra32ToGray8(BitmapSource BitmapSource) { Int32 PixelWidth = BitmapSource.PixelWidth; Int32 PixelHeight = BitmapSource.PixelHeight; Double DpiX = BitmapSource.DpiX; Double DpiY = BitmapSource.DpiY; PixelFormat InputPixelFormat = BitmapSource.Format; BitmapPalette InputPalette = BitmapSource.Palette; Int32 InputBitsPerPixel = BitmapSource.Format.BitsPerPixel; Int32 InputStride = PixelWidth * InputBitsPerPixel / 8; Byte[] InputPixelsArray = new Byte[InputStride * PixelHeight]; BitmapSource.CopyPixels(InputPixelsArray, InputStride, 0); PixelFormat PixelFormat = PixelFormats.Gray8; BitmapPalette Palette = null; Int32 BitsPerPixel = 8; Int32 Stride = PixelWidth * BitsPerPixel / 8; Byte[] A_PixelsArray = new Byte[InputStride * PixelHeight / 4]; Int32 i = 0; Int32 j = 3; while (i < InputPixelsArray.Length / 4) { A_PixelsArray[i] = InputPixelsArray[j]; i = i + 1; j = j + 4; } BitmapSource = BitmapSource.Create(PixelWidth, PixelHeight, DpiX, DpiY, PixelFormat, Palette, A_PixelsArray, Stride); return BitmapSource; }
将BitmapSource保存为PDF：
private void SaveFileAs(Object sender, RoutedEventArgs e) { SaveFileDialog SaveFileDialog = new SaveFileDialog(); SaveFileDialog.Filter = "PDF files (*.pdf)|*.pdf"; if (SaveFileDialog.ShowDialog() == true) { try { if (SaveFileDialog.FileName != null) { String DestinationPath = SaveFileDialog.FileName; FileStream DestinationFileStream = new FileStream(DestinationPath, FileMode.Create, FileAccess.Write, FileShare.Write); switch (SaveFileDialog.FilterIndex) { case 1: PdfDocument PdfDocument = new PdfDocument(); PdfPage PdfPage = new PdfPage(); PdfDocument.Pages.Add(PdfPage); XImage Image = XImage.FromBitmapSource(BitmapSource); XGraphics XGraphic = XGraphics.FromPdfPage(PdfDocument.Pages[0]); Double VerticalMargin = 20; Double HorizontalMargin = 20; Double Ratio = BitmapSource.Height / BitmapSource.Width; Double ImageWidth = PdfPage.Width - 2 * VerticalMargin; Double ImageHeight = Ratio * (PdfPage.Width - 2 * HorizontalMargin); XGraphic.DrawImage(Image, VerticalMargin, HorizontalMargin, ImageWidth, ImageHeight); PdfDocument.Save(DestinationFileStream); PdfDocument.Close(); DestinationFileStream.Close(); break; } } } catch (Exception Exception) { MessageBox.Show("Error: Could not write file to disk. Original error: ", Exception.Message, MessageBoxButton.OK, MessageBoxImage.Error); } } }