モノクロビットマップに変換して保存できるSaveMonoBitmapメソッド

色情報のあるビットマップを、モノクロ（２値）ビットマップに変換して、ビットマップファイルを保存できる、SaveMonoBitmapメソッドを作成しました。


using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.Drawing.Imaging;


public static void SaveMonoBitmap(Bitmap bmpColor, string strSaveBitmapPath)
{
    Bitmap bmpMono = Get1bppIndexedImage(bmpColor);
    bmpMono.SetResolution(200, 200);

    ImageCodecInfo imageCodecInfo;
    imageCodecInfo = GetEncoderInfo("image/bmp");

    EncoderParameters encoderParameters = new EncoderParameters(2);
    encoderParameters.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.ColorDepth, 1L);
    encoderParameters.Param[1] = new EncoderParameter(System.Drawing.Imaging.Encoder.Compression, (long)EncoderValue.CompressionCCITT4);

    bmpMono.Save(strSaveBitmapPath, imageCodecInfo, encoderParameters);
}

private static Bitmap Get1bppIndexedImage(Bitmap bmp)
{
    Bitmap monoBmp = new Bitmap(bmp.Width, bmp.Height, PixelFormat.Format1bppIndexed);
    BitmapData data = monoBmp.LockBits(
      new Rectangle(0, 0, monoBmp.Width, monoBmp.Height), ImageLockMode.ReadWrite, PixelFormat.Format1bppIndexed);

    for (int x = 0; x < bmp.Width; x++)
    {
        for (int y = 0; y < bmp.Height; y++)
        {
            if (bmp.GetPixel(x, y).GetBrightness() > 0.5)
                SetIndexedPixel(x, y, data, true);
            else
                SetIndexedPixel(x, y, data, false);
        }
    }

    monoBmp.UnlockBits(data);
    return monoBmp;
}

private static unsafe void SetIndexedPixel(int x, int y, BitmapData bmd, bool pixel)
{
    byte* p = (byte*)bmd.Scan0.ToPointer();
    int index = y * bmd.Stride + (x >> 3);
    byte mask = (byte)(0x80 >> (x & 0x7));

    if (pixel)
        p[index] |= mask;
    else
        p[index] &= (byte)(mask ^ 0xff);
}

private static ImageCodecInfo GetEncoderInfo(string mineType)
{
    ImageCodecInfo[] encs = ImageCodecInfo.GetImageEncoders();

    foreach (System.Drawing.Imaging.ImageCodecInfo enc in encs)
        if (enc.MimeType == mineType)
            return enc;

    return null;
}

using System;

using System.Collections.Generic;

using System.Text;

using System.Drawing;

using System.Drawing.Imaging;

public static void SaveMonoBitmap(Bitmap bmpColor, string strSaveBitmapPath)

{

Bitmap bmpMono = Get1bppIndexedImage(bmpColor);

bmpMono.SetResolution(200, 200);

ImageCodecInfo imageCodecInfo;

imageCodecInfo = GetEncoderInfo("image/bmp");

EncoderParameters encoderParameters = new EncoderParameters(2);

encoderParameters.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.ColorDepth, 1L);

encoderParameters.Param[1] = new EncoderParameter(System.Drawing.Imaging.Encoder.Compression, (long)EncoderValue.CompressionCCITT4);

bmpMono.Save(strSaveBitmapPath, imageCodecInfo, encoderParameters);

}

private static Bitmap Get1bppIndexedImage(Bitmap bmp)

{

Bitmap monoBmp = new Bitmap(bmp.Width, bmp.Height, PixelFormat.Format1bppIndexed);

BitmapData data = monoBmp.LockBits(

new Rectangle(0, 0, monoBmp.Width, monoBmp.Height), ImageLockMode.ReadWrite, PixelFormat.Format1bppIndexed);

for (int x = 0; x < bmp.Width; x++)

{

for (int y = 0; y < bmp.Height; y++)

{

if (bmp.GetPixel(x, y).GetBrightness() > 0.5)

SetIndexedPixel(x, y, data, true);

else

SetIndexedPixel(x, y, data, false);

}

monoBmp.UnlockBits(data);

return monoBmp;

}

private static unsafe void SetIndexedPixel(int x, int y, BitmapData bmd, bool pixel)

{

byte* p = (byte*)bmd.Scan0.ToPointer();

int index = y * bmd.Stride + (x >> 3);

byte mask = (byte)(0x80 >> (x & 0x7));

if (pixel)

p[index] |= mask;

else

p[index] &= (byte)(mask ^ 0xff);

}

private static ImageCodecInfo GetEncoderInfo(string mineType)

{

ImageCodecInfo[] encs = ImageCodecInfo.GetImageEncoders();

foreach (System.Drawing.Imaging.ImageCodecInfo enc in encs)

if (enc.MimeType == mineType)

return enc;

return null;

}

SaveMonoBitmapメソッドはこの形で利用できます。


Bitmap bmpColor = new Bitmap("c:\test.bmp");
SaveMonoBitmap(bmpColor, "c:\mono.bmp");

Bitmap bmpColor = new Bitmap("c:\test.bmp");

SaveMonoBitmap(bmpColor, "c:\mono.bmp");