创建8位映像

本文关键字：映像 8位 创建 | 更新日期: 2023-09-27 18:05:56

我正在尝试创建一个纯背景色的8位图像。看起来应该非常直接，但文件中的细节将其列为32位颜色深度。我错过了什么?

    public void CreateImage()
    {
        var bmpOut = new Bitmap(300, 300);
        var g = Graphics.FromImage(bmpOut);
        g.FillRectangle(new SolidBrush(Color.Gray), 0, 0, 300, 300);
        var stream = new MemoryStream();
        bmpOut.Save(stream, GetPngCodecInfo(), GetEncoderParameters());
        bmpOut.Save(@"C:'image.png", GetPngCodecInfo(), GetEncoderParameters());
    }
    public EncoderParameters GetEncoderParameters()
    {
        var parameters = new EncoderParameters();
        parameters.Param[0] = new EncoderParameter(Encoder.ColorDepth, 8);
        return parameters;
    }
    public ImageCodecInfo GetPngCodecInfo()
    {
        var encoders = ImageCodecInfo.GetImageEncoders();
        ImageCodecInfo codecInfo = null;
        foreach (var imageCodecInfo in encoders)
        {
            if (imageCodecInfo.FormatID != ImageFormat.Png.Guid)
                continue;
            codecInfo = imageCodecInfo;
            break;
        }
        return codecInfo;
    }

创建8位映像

使用此构造函数指定像素格式:http://msdn.microsoft.com/en-us/library/3z132tat.aspx

由于不能从索引像素格式创建图形，因此只能将原始像素写入8位图像。

Bitmap bitmap = new Bitmap(32, 32, PixelFormat.Format8bppIndexed);
var bitmapData = bitmap.LockBits(new Rectangle(Point.Empty, bitmap.Size), ImageLockMode.ReadWrite, bitmap.PixelFormat);
Random random=new Random();
byte[] buffer=new byte[bitmap.Width*bitmap.Height];
random.NextBytes(buffer);
Marshal.Copy(buffer,0,bitmapData.Scan0,buffer.Length);
bitmap.UnlockBits(bitmapData);
bitmap.Save("test.bmp",ImageFormat.Bmp);

你可以在WinForms上使用这样的代码:http://www.codeproject.com/Articles/17162/Fast-Color-Depth-Change-for-Bitmaps

或者如果你可以从WPF中引用这个类，那将会容易得多:http://msdn.microsoft.com/en-us/library/system.windows.media.imaging.formatconvertedbitmap (v = vs.85) . aspx

您还可以以更高的比特率创建图像，然后在保存之前将其转换为8位。这将允许您在创建图像时使用Graphics上下文。关于如何转换为8位的建议，请参阅这个问题:c# -如何将图像转换为8位彩色图像?

  • ImageExtensions.cs 

    using System.Runtime.InteropServices;
using System.Linq;
using System.Drawing.Imaging;
using System.Drawing;
using System;
public static partial class ImageExtensions {
    public static ColorPalette ToGrayScale(this ColorPalette palette) {
        var entries=palette.Entries;
        for(var i=entries.Length; i-->0; entries[i]=entries[i].ToGrayScale())
            ;
        return palette;
    }
    public static Color ToGrayScale(this Color color, double[] luminance=null) {
        var list=(luminance??new[] { 0.2989, 0.5870, 0.1140 }).ToList();
        var channel=new[] { color.R, color.G, color.B };
        var c=(byte)Math.Round(list.Sum(x => x*channel[list.IndexOf(x)]));
        return Color.FromArgb(c, c, c);
    }
    public static Bitmap To8bppIndexed(this Bitmap original) {
        var rect=new Rectangle(Point.Empty, original.Size);
        var pixelFormat=PixelFormat.Format8bppIndexed;
        var destination=new Bitmap(rect.Width, rect.Height, pixelFormat);
        using(var source=original.Clone(rect, PixelFormat.Format32bppArgb)) {
            var destinationData=destination.LockBits(rect, ImageLockMode.WriteOnly, pixelFormat);
            var sourceData=source.LockBits(rect, ImageLockMode.ReadOnly, source.PixelFormat);
            var destinationSize=destinationData.Stride*destinationData.Height;
            var destinationBuffer=new byte[destinationSize];
            var sourceSize=sourceData.Stride*sourceData.Height;
            var sourceBuffer=new byte[sourceSize];
            Marshal.Copy(sourceData.Scan0, sourceBuffer, 0, sourceSize);
            source.UnlockBits(sourceData);
            destination.Palette=destination.Palette.ToGrayScale();
            var list=destination.Palette.Entries.ToList();
            for(var y=destination.Height; y-->0; ) {
                for(var x=destination.Width; x-->0; ) {
                    var pixelIndex=y*destination.Width+x;
                    var sourceIndex=4*pixelIndex;
                    var color=
                        Color.FromArgb(
                            sourceBuffer[0+sourceIndex],
                            sourceBuffer[1+sourceIndex],
                            sourceBuffer[2+sourceIndex],
                            sourceBuffer[3+sourceIndex]
                            ).ToGrayScale();
                    destinationBuffer[pixelIndex]=(byte)list.IndexOf(color);
                }
            }
            Marshal.Copy(destinationBuffer, 0, destinationData.Scan0, destinationSize);
            destination.UnlockBits(destinationData);
        }
        return destination;
    }
}

在保存到文件之前调用bmpOut=bmpOut.To8bppIndexed();。

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