我在Google上尝试了很多搜索，然后在此处发布此问题。 我想在Win表单应用程序中使用RLE [Run Length Encoding]压缩来压缩8bpp位图 我发现的大多数结果来自VC ++代码，我可以使用GDI +执行压缩吗？ GDI +是否提供任何此类课程或方法？ 我在msdn找到了一个链接，但它没有多大帮助。
另外，我尝试使用“System.Drawing.Imaging.Encoder”编写下面的代码但是输出图像
具有相同的大小。
private void button1_Click(object sender, EventArgs e)
{
Bitmap myBitmap;
ImageCodecInfo myImageCodecInfo;
Encoder myEncoder;
EncoderParameter myEncoderParameter;
EncoderParameters myEncoderParameters;
// Create a Bitmap object based on a BMP file.
myBitmap = new Bitmap("D:\\8BppImage.bmp");
// Get an ImageCodecInfo object that represents the bmp codec.
myImageCodecInfo = GetEncoderInfo("image/bmp");
// Create an Encoder object based on the GUID
// for the Compression parameter category.
myEncoder = Encoder.Compression;
// Create an EncoderParameters object.
myEncoderParameters = new EncoderParameters(1);
myEncoderParameter = new EncoderParameter(
myEncoder,(long)EncoderValue.CompressionRle);
myEncoderParameters.Param[0] = myEncoderParameter;
myBitmap.Save("D:\\EncoderImg.bmp", myImageCodecInfo, myEncoderParameters);
}
private static ImageCodecInfo GetEncoderInfo(String mimeType)
{
int j;
ImageCodecInfo[] encoders;
encoders = ImageCodecInfo.GetImageEncoders();
for (j = 0; j < encoders.Length; ++j)
{
if (encoders[j].MimeType == mimeType)
return encoders[j];
}
return null;
}
我错过了什么吗？任何人都可以帮我这个吗？
答案 0 :(得分：2)
我已经在这个问题上使用RLE提交了在C＃中压缩8bpp图像的答案：How do I compress an image with Run-Length Encoding using C#?
我相信你的尝试不起作用，因为EncoderValue.CompressionRle只适用于.TIFF图像。
以下是用于执行压缩的代码：
private enum Compression
{
// others not necessary for the 8bpp compression, but left for reference
//BI_RGB = 0x0000,
BI_RLE8 = 0x0001,
//BI_RLE4 = 0x0002,
//BI_BITFIELDS = 0x0003,
//BI_JPEG = 0x0004,
//BI_PNG = 0x0005,
//BI_CMYK = 0x000B,
//BI_CMYKRLE8 = 0x000C,
//BI_CMYKRLE4 = 0x000D
}
private enum BitCount
{
// others not necessary for the 8bpp compression, but left for reference
//Undefined = (ushort)0x0000,
//TwoColors = (ushort)0x0001,
//Max16Colors = (ushort)0x0004,
Max256Colors = (ushort)0x0008,
//Max32KBColors = (ushort)0x0010,
//Max16MBColors = (ushort)0x0018,
//Max16MBColors_Compressed = (ushort)0x0020
}
private struct RleCompressedBmpHeader
{
// Everything before the HeaderSize is technically not part of the header (it's not included in the HeaderSize calculation)
/// <summary>
/// Size of the .bmp file.
/// Always header size (40), plus palette size, plus image size, plus pre-header size (14);
/// </summary>
public uint Size;
/// <summary>
/// Offset to start of image data in bytes from the start of the file
/// </summary>
public uint Offset;
/// <summary>
/// Size of this header in bytes. (Always 40)
/// </summary>
public uint HeaderSize; // 4 + 4 + 4 + 2 + 2 + 4 + 4 + 4 + 4 + 4 + 4
/// <summary>
/// Width of bitmap in pixels
/// </summary>
public int Width;
/// <summary>
/// Height of bitmap in pixels
/// </summary>
public int Height;
/// <summary>
/// Number of Planes (layers). Always 1.
/// </summary>
public ushort Planes;
/// <summary>
/// Number of bits that define each pixel and maximum number of colors
/// </summary>
public BitCount BitCount;
/// <summary>
/// Defines the compression mode of the bitmap.
/// </summary>
public Compression Compression;
/// <summary>
/// Size, in bytes, of image.
/// </summary>
public uint ImageSize;
// These shouldn't really be all that important
public uint XPixelsPerMeter;
public uint YPixelsPerMeter;
/// <summary>
/// The number of indexes in the color table used by this bitmap.
/// <para>0 - Use max available</para>
/// <para>If BitCount is less than 16, this is the number of colors used by the bitmap</para>
/// <para>If BitCount is 16 or greater, this specifies the size of the color table used to optimize performance of the system palette.</para>
/// </summary>
public uint ColorUsed;
/// <summary>
/// Number of color indexes that are required for displaying the bitmap. 0 means all color indexes are required.
/// </summary>
public uint ColorImportant;
public byte[] ToBytes()
{
var swap = BitConverter.IsLittleEndian;
var result = new List<byte>();
result.AddRange(new byte[] { 0x42, 0x4d }); // signature (BM)
result.AddRange(BitConverter.GetBytes(Size));
result.AddRange(new byte[4]); // reserved
result.AddRange(BitConverter.GetBytes(Offset));
result.AddRange(BitConverter.GetBytes(HeaderSize));
result.AddRange(BitConverter.GetBytes(Width));
result.AddRange(BitConverter.GetBytes(Height));
result.AddRange(BitConverter.GetBytes(Planes));
result.AddRange(BitConverter.GetBytes((ushort)BitCount));
result.AddRange(BitConverter.GetBytes((uint)Compression));
result.AddRange(BitConverter.GetBytes(ImageSize));
result.AddRange(BitConverter.GetBytes(XPixelsPerMeter));
result.AddRange(BitConverter.GetBytes(YPixelsPerMeter));
result.AddRange(BitConverter.GetBytes(ColorUsed));
result.AddRange(BitConverter.GetBytes(ColorImportant));
return result.ToArray();
}
}
public unsafe byte[] RunLengthEncodeBitmap(Bitmap bmp)
{
if (bmp.PixelFormat != PixelFormat.Format8bppIndexed) { throw new ArgumentException("The image must be in 8bppIndexed PixelFormat", "bmp"); }
var data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, PixelFormat.Format8bppIndexed);
List<byte> result = new List<byte>();
// Actual RLE algorithm. Bottom of image is first stored row, so start from bottom.
for (var rowIndex = bmp.Height - 1; rowIndex >= 0; rowIndex--)
{
byte? storedPixel = null;
var curPixelRepititions = 0;
var imageRow = (byte*)data.Scan0.ToPointer() + (rowIndex * data.Stride);
for (var pixelIndex = 0; pixelIndex < bmp.Width; pixelIndex++)
{
var curPixel = imageRow[pixelIndex];
if (!storedPixel.HasValue)
{
curPixelRepititions = 1;
storedPixel = curPixel;
}
else if (storedPixel.Value != curPixel || curPixelRepititions == 255)
{
result.Add(Convert.ToByte(curPixelRepititions));
result.Add(storedPixel.Value);
curPixelRepititions = 1;
storedPixel = curPixel;
}
else
{
curPixelRepititions++;
}
}
if (curPixelRepititions > 0)
{
result.Add(Convert.ToByte(curPixelRepititions));
result.Add(storedPixel.Value);
}
if (rowIndex == 0)
{
// EOF flag
result.Add(0x00);
result.Add(0x01);
}
else
{
// End of Line Flag
result.Add(0x00);
result.Add(0x00);
}
}
bmp.UnlockBits(data);
var paletteSize = (uint)bmp.Palette.Entries.Length * 4;
var header = new RleCompressedBmpHeader();
header.HeaderSize = 40;
header.Size = header.HeaderSize + paletteSize + (uint)result.Count + 14;
header.Offset = header.HeaderSize + 14 + paletteSize; // total header size + palette size
header.Width = bmp.Width;
header.Height = bmp.Height;
header.Planes = 1;
header.BitCount = BitCount.Max256Colors;
// as far as I can tell, PixelsPerMeter are not terribly important
header.XPixelsPerMeter = 0x10000000;
header.YPixelsPerMeter = 0x10000000;
header.Compression = Compression.BI_RLE8;
header.ColorUsed = 256;
header.ColorImportant = 0; // use all available colors
header.ImageSize = header.HeaderSize + (uint)result.Count;
var headerBytes = header.ToBytes();
var paletteBytes = ConvertPaletteToBytes(bmp.Palette);
return headerBytes.Concat(paletteBytes).Concat(result).ToArray();
}
private byte[] ConvertPaletteToBytes(ColorPalette colorPalette)
{
return colorPalette.Entries.SelectMany(c => new byte[]
{
c.B,
c.G,
c.R,
0
}).ToArray();
}