c# - 从 1bpp 位图制作 1bpp PCX 时遇到问题

Question

我有这个类适用于 8 bpp 位图到 pcx，但我无法让它适用于 1 bpp。

图像开始是这样的：

但是在第 27 行之后生成的 PCX 是黑色的，如 IrfanView 中所示：

谁能帮我发现明显的错误？

顺便说一句，用法是Pcx.SavePCX("AOut.pcx", new Bitmap("A.bmp"));

using System;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Runtime.InteropServices;

namespace Imaging
{
    public sealed class Pcx
    {
        private static void WriteWord(Stream stream, int data)
        {
            stream.WriteByte((byte) (data & 0xFF));
            stream.WriteByte((byte) ((data >> 8) & 0xFF));
        }

        public static void SavePCX(Stream pcxStream, Bitmap bmp)
        {
            if (bmp.PixelFormat != PixelFormat.Format1bppIndexed)
            {
                throw new Exception("Can only PCX bitmaps that are 1bpp indexed");
            }

            var data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, bmp.PixelFormat);
            try
            {
                {
                    //header
                    pcxStream.WriteByte(10); //    char manufacturer;
                    pcxStream.WriteByte(5); //char version;
                    pcxStream.WriteByte(1); //char encoding;
                    pcxStream.WriteByte(1); // char bpp;
                    pcxStream.WriteByte(0);
                    pcxStream.WriteByte(0); //char xmin[2];
                    pcxStream.WriteByte(0);
                    pcxStream.WriteByte(0); //char ymin[2];
                    WriteWord(pcxStream, bmp.Width - 1); // char xmax[2];
                    WriteWord(pcxStream, bmp.Height - 1); //char ymax[2];

                    WriteWord(pcxStream, 72); //word(pcx->hdpi, 72);
                    WriteWord(pcxStream, 72); // word(pcx->vdpi, 72);
                    for (var i = 0; i < 16*3; i++) //4bpp palette
                    {
                        pcxStream.WriteByte(0);
                    }
                    pcxStream.WriteByte(0); // pcx->res = 0;
                    pcxStream.WriteByte(1); // pcx->nplanes = 1;
                    WriteWord(pcxStream, bmp.Width); // word(pcx->bytesperline, width / 2);
                    WriteWord(pcxStream, 0); //word(pcx->palletteinfo, 0);
                    WriteWord(pcxStream, 0); //word(pcx->hscrn, 0);
                    WriteWord(pcxStream, 0); //word(pcx->vscrn, 0);

                    for (var i = 0; i < 54; i++) //memset(pcx->filler, 0, 54);
                    {
                        pcxStream.WriteByte(0);
                    }
                } //end of header

                {
                    //read all bytes to an array
                    var baseLine = data.Scan0;
                    // Declare an array to hold the bytes of the bitmap.
                    var byteLength = bmp.Width*bmp.Height;
                    var bytes = new byte[byteLength];

                    // Copy the RGB values into the array.
                    for (var y = 0; y < data.Height; y++)
                    {
                        var lineOffset = y*data.Stride;
                        Debug.WriteLine("Y={0}, Offset={1}", y, lineOffset);
                        for (var x = 0; x < data.Width; x++)
                        {
                            bytes[y*bmp.Width + x] = Marshal.ReadByte(baseLine, lineOffset + x);
                        }
                    }

                    var baseIdx = 0;
                    var end = byteLength;
                    var run = 0;
                    var ldata = -1;
                    byte ld;

                    while (baseIdx < end)
                    {
                        //if it matches, increase the run by 1 up to max of 63
                        if ((bytes[baseIdx] == ldata) && (run < 63)) run++;
                        else
                        {
                            //write data
                            if (run != 0) //not first run
                            {
                                ld = (byte) ldata;
                                if ((run > 1) || (ld >= 0xC0)) pcxStream.WriteByte((byte) (0xC0 | run));
                                pcxStream.WriteByte(ld);
                            }
                            run = 1;
                        }
                        ldata = bytes[baseIdx];
                        baseIdx++;
                    }
                    ld = (byte) ((ldata >> 4) | (ldata << 4));
                    if ((run > 1) || (ld >= 0xC0)) pcxStream.WriteByte((byte) (0xC0 | run));
                    pcxStream.WriteByte(ld);
                }
            }
            finally
            {
                bmp.UnlockBits(data);
            }
        }

        public static void SavePCX(string fileName, Bitmap bbp1Bmp)
        {
            using (var fstest = new FileStream(fileName, FileMode.Create, FileAccess.Write))
            {
                SavePCX(fstest, bbp1Bmp);
            }
        }
    }
}

Answer 1

通过使用每行的字节数来解决它data.Stride，并使用 stride 作为宽度而不是宽度从 1bpp 读取字节。

public static void SavePCX(Stream pcxStream, Bitmap bmp)
{
    if (bmp.PixelFormat != PixelFormat.Format1bppIndexed)
    {
        throw new Exception("Can only PCX bitmaps that are 1bpp indexed");
    }

    var data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, bmp.PixelFormat);
    try
    {
        {
            //header
            pcxStream.WriteByte(10); //    char manufacturer;
            pcxStream.WriteByte(5); //char version;
            pcxStream.WriteByte(1); //char encoding;
            pcxStream.WriteByte(1); // char bpp;
            pcxStream.WriteByte(0);
            pcxStream.WriteByte(0); //char xmin[2];
            pcxStream.WriteByte(0);
            pcxStream.WriteByte(0); //char ymin[2];
            WriteWord(pcxStream, bmp.Width - 1); // char xmax[2];
            WriteWord(pcxStream, bmp.Height - 1); //char ymax[2];

            WriteWord(pcxStream, 72); //word(pcx->hdpi, 72);
            WriteWord(pcxStream, 72); // word(pcx->vdpi, 72);
            for (var i = 0; i < 16*3; i++) //4bpp palette
            {
                pcxStream.WriteByte(0);
            }
            pcxStream.WriteByte(0); // pcx->res = 0;
            pcxStream.WriteByte(1); // pcx->nplanes = 1;
            WriteWord(pcxStream, data.Stride); // word(pcx->bytesperline, width / 2);
            WriteWord(pcxStream, 0); //word(pcx->palletteinfo, 0);
            WriteWord(pcxStream, 0); //word(pcx->hscrn, 0);
            WriteWord(pcxStream, 0); //word(pcx->vscrn, 0);

            for (var i = 0; i < 54; i++) //memset(pcx->filler, 0, 54);
            {
                pcxStream.WriteByte(0);
            }
        } //end of header

        {
            //read all bytes to an array
            var baseLine = data.Scan0;
            // Declare an array to hold the bytes of the bitmap.
            var byteLength = data.Stride*data.Height;
            var bytes = new byte[byteLength];

            // Copy the RGB values into the array.
            for (var y = 0; y < data.Height; y++)
            {
                var lineOffset = y*data.Stride;
                Debug.WriteLine("Y={0}, Offset={1}", y, lineOffset);
                for (var x = 0; x < data.Stride; x++)
                {
                    bytes[y*data.Stride + x] = Marshal.ReadByte(baseLine, lineOffset + x);
                }
            }

            var baseIdx = 0;
            var end = byteLength;
            var run = 0;
            var ldata = -1;
            byte ld;

            while (baseIdx < end)
            {
                //if it matches, increase the run by 1 up to max of 63
                if ((bytes[baseIdx] == ldata) && (run < 63)) run++;
                else
                {
                    //write data
                    if (run != 0) //not first run
                    {
                        ld = (byte) ldata;
                        if ((run > 1) || (ld >= 0xC0)) pcxStream.WriteByte((byte) (0xC0 | run));
                        pcxStream.WriteByte(ld);
                    }
                    run = 1;
                }
                ldata = bytes[baseIdx];
                baseIdx++;
            }
            ld = (byte) ((ldata >> 4) | (ldata << 4));
            if ((run > 1) || (ld >= 0xC0)) pcxStream.WriteByte((byte) (0xC0 | run));
            pcxStream.WriteByte(ld);
        }
    }
    finally
    {
        bmp.UnlockBits(data);
    }
}