ClassLibraryWeiBao/QR二维码/Windows/Render/WriteableBitmapExtension.cs

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using System;
using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Runtime.InteropServices;

namespace Gma.QrCodeNet.Encoding.Windows.Render
{
    internal static class WriteableBitmapExtension
    {
        /// <summary>
        /// Clear all pixel with given color.
        /// </summary>
        /// <param name="wBitmap">Must not be null, or pixel width, pixel height equal to zero</param>
        /// <exception>Exception should be expect with null writeablebitmap or pixel width, height equal to zero.</exception>
        internal static void Clear(this WriteableBitmap wBitmap, Color color)
        {
            if (!(wBitmap.Format == PixelFormats.Pbgra32 || wBitmap.Format == PixelFormats.Gray8))
                return;
            byte[] col = ConvertColor(wBitmap.Format, color);

            //Currently only support two PixelFormat.
            int sizeOfColor = wBitmap.Format == PixelFormats.Pbgra32 ? 4 : 1;

            int pixelW = wBitmap.Format == PixelFormats.Gray8 ? wBitmap.BackBufferStride : wBitmap.PixelWidth;
            int pixelH = wBitmap.PixelHeight;
            int totalPixels = pixelW * pixelH;

            wBitmap.Lock();
            unsafe
            {
                byte* pixels = (byte*)wBitmap.BackBuffer;
                int length = col.Length;
                //Draw first dot color. 
                for (int index = 0; index < length; index++)
                {
                    *(pixels + index) = col[index];
                }

                int pixelIndex = 1;
                int blockPixels = 1;
                //Expand to all other pixels with Log(n) process. 
                while (pixelIndex < totalPixels)
                {
                    CopyUnmanagedMemory(pixels, 0, pixels, pixelIndex * sizeOfColor, blockPixels * sizeOfColor);

                    pixelIndex += blockPixels;
                    blockPixels = Math.Min(2 * blockPixels, totalPixels - pixelIndex);
                }
            }
            wBitmap.AddDirtyRect(new Int32Rect(0, 0, wBitmap.PixelWidth, wBitmap.PixelHeight));
            wBitmap.Unlock();

        }

        /// <summary>
        /// Draw rectangle with given color.
        /// </summary>
        /// <param name="wBitmap">Must not be null, or pixel width, pixel height equal to zero</param>
        /// <exception>Exception should be expect with null writeablebitmap or pixel width, height equal to zero.</exception>