loadbmp.java

《Java实例入门》所有实例的源代码。所有的源文件都是.java文件

public Image loadbitmap (String sdir, String sfile){
	Image image;
 	System.out.println("loading:"+sdir+sfile);
 	try
     	{
     		FileInputStream fs=new FileInputStream(sdir+sfile);
     		int bflen=14; // 14 字节 BITMAPFILEHEADER
     		byte bf[]=new byte[bflen];
     		fs.read(bf,0,bflen);
     		int bilen=40; // 40 字节 BITMAPINFOHEADER
     		byte bi[]=new byte[bilen];
     		fs.read(bi,0,bilen);

		// 解释数据。
     		int nsize = (((int)bf[5]&0xff)<<24)
     		|(((int)bf[4]&0xff)<<16)|(((int)bf[3]&0xff)<<8)
     		|(int)bf[2]&0xff;
     		System.out.println("File type is :"+(char)bf[0]+(char)bf[1]);
     		System.out.println("Size of file is :"+nsize);
		
		int nbisize = (((int)bi[3]&0xff)<<24)
		|(((int)bi[2]&0xff)<<16)|(((int)bi[1]&0xff)<<8)
		|(int)bi[0]&0xff;
     		System.out.println("Size of bitmapinfoheader is :"+nbisize);

     		int nwidth = (((int)bi[7]&0xff)<<24)
     		|(((int)bi[6]&0xff)<<16)|(((int)bi[5]&0xff)<<8)
     		|(int)bi[4]&0xff;
     		System.out.println("Width is :"+nwidth);
		
		int nheight = (((int)bi[11]&0xff)<<24)
		|(((int)bi[10]&0xff)<<16)|(((int)bi[9]&0xff)<<8)
		|(int)bi[8]&0xff;
     		System.out.println("Height is :"+nheight);
			
		int nplanes = (((int)bi[13]&0xff)<<8) | (int)bi[12]&0xff;
		System.out.println("Planes is :"+nplanes);

     		int nbitcount = (((int)bi[15]&0xff)<<8) | (int)bi[14]&0xff;
     		System.out.println("BitCount is :"+nbitcount);

     		// 查找表明压缩的非零值
     		int ncompression = (((int)bi[19])<<24)
     		|(((int)bi[18])<<16)|(((int)bi[17])<<8)
     		|(int)bi[16];
     		System.out.println("Compression is :"+ncompression);

     		int nsizeimage = (((int)bi[23]&0xff)<<24)
     		|(((int)bi[22]&0xff)<<16)|(((int)bi[21]&0xff)<<8)
     		|(int)bi[20]&0xff;
     		System.out.println("SizeImage is :"+nsizeimage);

     		int nxpm = (((int)bi[27]&0xff)<<24)
     		|(((int)bi[26]&0xff)<<16)|(((int)bi[25]&0xff)<<8)
     		|(int)bi[24]&0xff;
     		System.out.println("X-Pixels per meter is :"+nxpm);

     		int nypm = (((int)bi[31]&0xff)<<24)
     		|(((int)bi[30]&0xff)<<16)|(((int)bi[29]&0xff)<<8)
     		|(int)bi[28]&0xff;
     		System.out.println("Y-Pixels per meter is :"+nypm);

     		int nclrused = (((int)bi[35]&0xff)<<24)
     		|(((int)bi[34]&0xff)<<16)|(((int)bi[33]&0xff)<<8)
     		|(int)bi[32]&0xff;
     		System.out.println("Colors used are :"+nclrused);

     		int nclrimp = (((int)bi[39]&0xff)<<24)
     		|(((int)bi[38]&0xff)<<16)|(((int)bi[37]&0xff)<<8)
     		|(int)bi[36]&0xff;
     		System.out.println("Colors important are :"+nclrimp);

     		if (nbitcount==24)
  		{
  			// 24 位格式不包含调色板数据，但扫描行被补足到4个字节。
  			int npad = (nsizeimage / nheight) - nwidth * 3;
  			int ndata[] = new int [nheight * nwidth];
  			byte brgb[] = new byte [( nwidth + npad) * 3 * nheight];
  			fs.read (brgb, 0, (nwidth + npad) * 3 * nheight);
  			int nindex = 0;
  			for (int j = 0; j < nheight; j++)
      			{
      				for (int i = 0; i < nwidth; i++)
   				{
   					ndata [nwidth * (nheight - j - 1) + i] =(255&0xff)<<24 
   					|(((int)brgb[nindex+2]&0xff)<<16)
   					|(((int)brgb[nindex+1]&0xff)<<8)
   					|(int)brgb[nindex]&0xff;
   					//System.out.println("Encoded Color at ("+i+","+j+")is:"
   					+nrgb+" (R,G,B)= ("+((int)(brgb[2]) & 0xff)+",
   					"+((int)brgb[1]&0xff)+","+((int)brgb[0]&0xff)+")");
   					nindex += 3;
   				}
      				nindex += npad;
      			}

			  image = createImage( new MemoryImageSource (nwidth, nheight,ndata, 0, nwidth));
  		}
     		else if (nbitcount == 8)
  		{
  			// 必须确定颜色数。如果 clrsused 参数大于 0，
  			// 则颜色数由它决定。如果它等于 0，则根据
  			// bitsperpixel 计算颜色数。
  			int nNumColors = 0;
  			if (nclrused > 0)
      			{
      				nNumColors = nclrused;
      			}
  			else
      			{
      				nNumColors = (1&0xff)<<nbitcount;
      			}
  			System.out.println("The number of Colors is"+nNumColors);

			// 某些位图不计算 sizeimage 域，请找出
  			// 这些情况并对它们进行修正。
  			if (nsizeimage == 0)
      			{
      				nsizeimage = ((((nwidth*nbitcount)+31) & ~31 ) >> 3);
      				nsizeimage *= nheight;
      				System.out.println("nsizeimage (backup) is"+nsizeimage);
      			}

  			// 读取调色板颜色。
  			int npalette[] = new int [nNumColors];
  			byte bpalette[] = new byte [nNumColors*4];
  			fs.read (bpalette, 0, nNumColors*4);
  			int nindex8 = 0;
  			for (int n = 0; n < nNumColors; n++)
      			{
      				npalette[n] = (255&0xff)<<24 
      				|(((int)bpalette[nindex8+2]&0xff)<<16)
      				|(((int)bpalette[nindex8+1]&0xff)<<8)
      				|(int)bpalette[nindex8]&0xff;
      				// System.out.println ("Palette Color "+n+
      				" is:"+npalette[n]+" (res,R,G,B)= 
      				("+((int)(bpalette[nindex8+3]) & 0xff)+","+
      				((int)(bpalette[nindex8+2]) & 0xff)+","+
      				((int)bpalette[nindex8+1]&0xff)+","+
      				((int)bpalette[nindex8]&0xff)+")");
      				nindex8 += 4;
      			}

  			// 读取图像数据（实际上是调色板的索引）
  			// 扫描行仍被补足到 4 个字节。
  			int npad8 = (nsizeimage / nheight) - nwidth;
  			System.out.println("nPad is:"+npad8);

  			int ndata8[] = new int [nwidth*nheight];
  			byte bdata[] = new byte [(nwidth+npad8)*nheight];
  			fs.read (bdata, 0, (nwidth+npad8)*nheight);
  			nindex8 = 0;
  			for (int j8 = 0; j8 < nheight; j8++)
      			{
      				for (int i8 = 0; i8 < nwidth; i8++)
   				{
   					ndata8 [nwidth*(nheight-j8-1)+i8] =
   					npalette [((int)bdata[nindex8]&0xff)];
   					nindex8++;
   				}
      				nindex8 += npad8;
      			}

			image = createImage(new MemoryImageSource 
			(nwidth, nheight,ndata8, 0, nwidth));
  		}
     		else
  		{
  			System.out.println ("Not a 24-bit or 8-bit Windows 
  			Bitmap, aborting...");
  			image = (Image)null;
  		}

     		fs.close();
     		return image;
     	}
 	catch (Exception e)
     	{
     		System.out.println("Caught exception in loadbitmap!");
     	}
 	return (Image) null;
 }