java读取bmp图像文件

一。BMP格式说明

文件头结构（14字节0xE）

struct BITMAPFILEHEADER {

WORD bfType; //文件标志, 如果为BMP文件，就为“BM”

DWORD bfSize; //文件大小

DWORD Reserved; //保留

DWORD bfOffBits; //数据偏移

};

位图信息结构（40字节0x28）

struct BITMAPINFOHEADER {

DWORD biSize; //信息头大小，即本结构的大小

long biWidth; //位图宽,像素

long biHeight; //位图高,像素

WORD biPlanes; //目标设备的位平面数,只能为1

WORD biBitCount; //每个像素的位数

DWORD biCompression; //位图压缩方式

DWORD biSizeImage; //位图数据区的大小; 对BI_RGB压缩方式,以字节为单位

long biXPelsPerMeter; //水平方向每米和像素个数

long biYPelsPerMeter; //垂直方向每米和像素个数

DWORD biClrUsed; //调色板中实际使用的颜色数

DWORD biClrImportant; //使用位图时必需的颜色数

};

位图信息结构详细说明：

biBitCount
每个像素的位数, 下面的值有意义：

0，用在JPEG格式中；

1，单色图，调色板中含两种颜色；

4，16色图；

8，256色图；

16，64K图，一般没有调色板，图像数据中每2个字节表示一个像素，5或6位表示一个RGB分量

24，16M真彩图，没有调色板，图像数据中每3个字节表示一个像素，每个字节表示一个RGB分量；

32，4G真彩色图，一般没有调色板

biCompression
这个值表示图像的压缩格式：

BI_RGB，普通格式无压缩

BI_RLE，使用 run-length encoded 压缩，每个像素占8 个bits;

BI_BITFIELDS，数据未压缩，但本结构后有一个32bits 的整数，作为RGB 3 种颜色的掩码，用于16 位图的32位图

BI_JPEG，jpeg压缩

这个值几乎总为0

biClrUsed
调色板中实际使用的颜色数，对于2、16、256色图，这个域通常为0，表示使用biBitCount 确定的全部颜色；唯一例外是当使用的颜色数目小于指定的颜色数目的最大值

biClrImportant
显示位图时必需的颜色数，作为调色板管理策略的参考参数之一，通常被使用的0 值表示所有的颜色都是必需的

位图颜色表（调色板）

结构形式　

RGBQUAD　｛

　BYTE　rgbBlue; //兰色的比例

BYTE rgbGreen, //绿色的比例

BYTE rgbRed; //红色的比例

BYTE rgbReserved //一般为0

}

颜色表中的颜色顺序是BGR，而不是平常的RGB

最后是图像数据

位图数据是从图像的最下面一行开始的逐行向上存储的，也就是说，等于把图像倒过来然后在逐行扫描。并且，位图数据中每个扫描行的字节数必须是4的倍数。如果不足要用0补齐。

（biWidth * 每个像素所占字节数+3）&0xfffffffc;

用此计算可得到每个扫描行的实际字节数，如果为16位图，则要用这个公式

（（biWidth * (每个像素所占字节数=2)+3）&0xfffffffc）/ 2;

如果没有调色板，位图数据中每个像素的颜色顺序是BGR

二。java的Image等类不直接支持bmp图像文件读取。需要自行分析文件格式，以读取文件相关数据。 大致上bmp文件有2大类，没有Color panel（16bit，24bit，32bit）和有Color Panel的（单色，4bit，8bit）。其中16bit又比较特殊每5个bit为一个单元色，需要乘8（或<<3）转换成8bit单元色数据。 以下为源码：

package BMP;

import java.awt.Image;
import java.awt.Toolkit;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.awt.image.MemoryImageSource;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

//import com.sun.image.codec.jpeg.JPEGCodec;
//import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class BmpParse {

private File srcImage;
private Graphics2D graph;

public BmpParse(String imagefile) {
srcImage = new File(imagefile);
}

public BmpParse(File imagefile) {
srcImage = imagefile;
}

public boolean Reader(Graphics2D graph) {
Image image; //target image

if (!srcImage.exists())
{
System.out.println("bmp file is not exist!");
return false;
}

try {
FileInputStream fs = new FileInputStream(srcImage);
int bflen = 14;
byte bf[] = new byte[bflen];
fs.read(bf, 0, bflen); //read 14 byte the head of bmp file
int bilen = 40;
byte bi[] = new byte[bilen];
fs.read(bi, 0, bilen); //read 40 byte the head of bmp info

// /u83B7取一些重要数据
int nwidth = ( ( (int) bi[7] & 0xff) << 24) //width of source file
| ( ( (int) bi[6] & 0xff) << 16)
| ( ( (int) bi[5] & 0xff) << 8)
| (int) bi[4] & 0xff;
System.out.println("Width:" + nwidth);
int nheight = ( ( (int) bi[11] & 0xff) << 24) //heigth of source file
| ( ( (int) bi[10] & 0xff) << 16)
| ( ( (int) bi[9] & 0xff) << 8)
| (int) bi[8] & 0xff;
System.out.println("Heigth:" + nheight);
//bits of source file
int nbitcount = ( ( (int) bi[15] & 0xff) << 8) | (int) bi[14] & 0xff;
System.out.println("Bits Count:" + nbitcount);
//size of source file
int nsizeimage = ( ( (int) bi[23] & 0xff) << 24)
| ( ( (int) bi[22] & 0xff) << 16)
| ( ( (int) bi[21] & 0xff) << 8)
| (int) bi[20] & 0xff;
System.out.println("Size:" + nsizeimage);

//parse the 24 bit bmp file
if (nbitcount == 24) {
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;
nindex += 3;
}
nindex += npad;
}
Toolkit kit = Toolkit.getDefaultToolkit();
image = kit.createImage(new MemoryImageSource(nwidth, nheight,
ndata, 0, nwidth));
System.out.println("get image from bmp file");
}
else {
image = (Image)null;
System.out.println("not 24 bit bitmap, failed!");
return false;
}
fs.close(); //close input stream

// start extract image file
int wideth = image.getWidth(null);
int height = image.getHeight(null);
BufferedImage tag = new BufferedImage(wideth, height,
BufferedImage.TYPE_INT_RGB);

/* tag.getGraphics().drawImage(image, 0, 0, wideth / 2, height / 2, null);
FileOutputStream out = new FileOutputStream("newfile.jpg");
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
encoder.encode(tag);
out.close(); //close output stream
*/
graph.drawImage(image, 0, 0, wideth, height, null);
}
catch (Exception e) {
e.printStackTrace();
return false;
}

return true;
}

/**
loadbitmap() method converted from Windows C code.
Reads only uncompressed 24- and 8-bit images. Tested with
images saved using Microsoft Paint in Windows 95. If the image
is not a 24- or 8-bit image, the program refuses to even try.
I guess one could include 4-bit images by masking the byte
by first 1100 and then 0011. I am not really
interested in such images. If a compressed image is attempted,
the routine will probably fail by generating an IOException.
Look for variable ncompression to be different from 0 to indicate
compression is present.

Arguments:
sdir and sfile are the result of the FileDialog()
getDirectory() and getFile() methods.

Returns:
Image Object, be sure to check for (Image)null !!!! */

public Image loadbitmap(Graphics2D graph) {
Image image;
System.out.println("loading:" + srcImage.getName());
try {
FileInputStream fs = new FileInputStream(srcImage);
int bflen = 14; // 14 byte BITMAPFILEHEADER
byte bf[] = new byte[bflen];
fs.read(bf, 0, bflen);
int bilen = 40; // 40-byte BITMAPINFOHEADER
byte bi[] = new byte[bilen];
fs.read(bi, 0, bilen);

// Interperet data.
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);

// Head info data
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);

// number of planes in this bitmap
int nplanes = ( ( (int) bi[13] & 0xff) << 8) | (int) bi[12] & 0xff;
System.out.println("Planes is :" + nplanes);

// bits per pixel used to store palette entry
// information. this also identifies in an indirect way
// the number of possible colors. possible values are: 1, 4, 8, 16, 24, 32
int nbitcount = ( ( (int) bi[15] & 0xff) << 8) | (int) bi[14] & 0xff;
System.out.println("BitCount is :" + nbitcount);

// Look for non-zero values to indicate compression
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);

// Some bitmaps do not have the sizeimage field calculated
// Ferret out these cases and fix 'em.
if (nsizeimage == 0) {
nsizeimage = ( ( ( (nwidth * nbitcount) + 31) & ~31) >> 3);
nsizeimage *= nheight;
System.out.println("nsizeimage (backup) is" + nsizeimage);
}

if (nbitcount == 32)
{
// No Palatte data for 32-bit format but scan lines are
// padded out to even 4-byte boundaries.
int npad = (nsizeimage / nheight) - nwidth * 4;
int ndata[] = new int[nheight * nwidth];
byte brgb[] = new byte[ (nwidth + npad) * 4 * nheight];
fs.read(brgb, 0, (nwidth + npad) * 4 * 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:" + brgb + " (R,G,B)= ("
+ ( (int) (brgb[2]) & 0xff) + ","
+ ( (int) brgb[1] & 0xff) + ","
+ ( (int) brgb[0] & 0xff) + ")"); */
nindex += 4;
}
nindex += npad;
}

image = Toolkit.getDefaultToolkit().createImage
(new MemoryImageSource(nwidth, nheight,
ndata, 0, nwidth));
}
else if (nbitcount == 24) {
// No Palatte data for 24-bit format but scan lines are
// padded out to even 4-byte boundaries.
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:" + brgb + " (R,G,B)= ("
+ ( (int) (brgb[2]) & 0xff) + ","
+ ( (int) brgb[1] & 0xff) + ","
+ ( (int) brgb[0] & 0xff) + ")");*/
nindex += 3;
}
nindex += npad;
}

image = Toolkit.getDefaultToolkit().createImage
(new MemoryImageSource(nwidth, nheight,
ndata, 0, nwidth));
}
else if (nbitcount == 16) {
// No Palatte data for 16-bit format but scan lines are
// padded out to even 4-byte boundaries.
int npad = (nsizeimage / nheight) - nwidth * 2;
int ndata[] = new int[nheight * nwidth];
byte brgb[] = new byte[ (nwidth + npad) * 2 * nheight];
fs.read(brgb, 0, (nwidth + npad) * 2 * 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 + 1] >>> 2) & 0x3f) | 0x60)<<3 << 16)
| ( ( ( (int) (((brgb[nindex + 1]&0x3)<<3) | ((brgb[nindex]&0xe0)>>>5))) | 0x60)<<3 << 8)
| ( ( ( (int) brgb[nindex] & 0x1f) | 0x60)<<3);

nindex += 2;
}
nindex += npad;
}

image = Toolkit.getDefaultToolkit().createImage
(new MemoryImageSource(nwidth, nheight,
ndata, 0, nwidth));
}
else if (nbitcount == 8) {
// Have to determine the number of colors, the clrsused
// parameter is dominant if it is greater than zero. If
// zero1, calculate colors based on bitsperpixel.
int nNumColors = 0;
if (nclrused > 0) {
nNumColors = nclrused;
}
else {
nNumColors = (1 & 0xff) << nbitcount;
}
System.out.println("The number of Colors is" + nNumColors);

// Read the palatte colors.
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
= (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
+ " (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;
}

// Read the image data (actually indices into the palette)
// Scan lines are still padded out to even 4-byte
// boundaries.
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 = Toolkit.getDefaultToolkit().createImage
(new MemoryImageSource(nwidth, nheight,
ndata8, 0, nwidth));
}
else if (nbitcount == 4) {
// Have to determine the number of colors, the clrsused
// parameter is dominant if it is greater than zero. If
// zero1, calculate colors based on bitsperpixel.
int nNumColors = 0;
if (nclrused > 0) {
nNumColors = nclrused;
}
else {
nNumColors = (1 & 0xff) << nbitcount;
}
System.out.println("The number of Colors is" + nNumColors);

// Read the palatte colors.
int npalette[] = new int[nNumColors];
byte bpalette[] = new byte[nNumColors * 4];
fs.read(bpalette, 0, nNumColors * 4);
int nindex4 = 0;
for (int n = 0; n < nNumColors; n++) {
npalette
= (255 & 0xff) << 24
| ( ( (int) bpalette[nindex4 + 2] & 0xff) << 16)
| ( ( (int) bpalette[nindex4 + 1] & 0xff) << 8)
| (int) bpalette[nindex4] & 0xff;
/* System.out.println("Palette Color " + n
+ " is:" + npalette
+ " (res,R,G,B)= ("
+ ( (int) (bpalette[nindex8 + 3]) & 0xff) + ","
+ ( (int) (bpalette[nindex8 + 2]) & 0xff) + ","
+ ( (int) bpalette[nindex8 + 1] & 0xff) + ","
+ ( (int) bpalette[nindex8] & 0xff) + ")"); */
nindex4 += 4;
}

// Scan line is padded with zeroes to be a multiple of four bytes
int scanLineSize = ( ( (nwidth * nbitcount) + 31) & ~31) >> 3;

// Read the image data (actually indices into the palette)
// Scan lines are still padded out to even 4-byte
// boundaries.
//int npad4 = (nsizeimage / nheight) - nwidth / 2;
/*int npad4 = 0;
if ((nwidth%2) == 0)
npad4 = scanLineSize - nwidth/2;
else
npad4 = scanLineSize - nwidth/2 - 1;
System.out.println("nPad is:" + npad4);*/

int ndata4[] = new int[nwidth * nheight];
//byte bdata[] = new byte[ scanLineSize * nheight];
byte blinedata[] = new byte[scanLineSize];
//fs.read(bdata, 0, scanLineSize * nheight);
nindex4 = 0;
for (int j4 = 0; j4 < nheight; j4++) {
fs.read(blinedata, 0, scanLineSize);
nindex4 = 0;

for (int i4 = 0; i4 < nwidth; i4++) {

if (nwidth * (nheight - j4 - 1) + i4 > nwidth * nheight-1)
break;
if (nindex4 > scanLineSize * nheight - 1)
break;

for (int pixPerByte = 0; pixPerByte < 2; pixPerByte++)
{
if (pixPerByte == 0)
{
ndata4[nwidth * (nheight - j4 - 1) + i4] =
npalette[ ( (int) (blinedata[nindex4]>>4) & 0xf)];
i4++;
if (i4 >= nwidth)
break;
}
else
{
ndata4[nwidth * (nheight - j4 - 1) + i4] =
npalette[ ( (int) blinedata[nindex4] & 0xf)];
}
}

nindex4++;
}
}

image = Toolkit.getDefaultToolkit().createImage
(new MemoryImageSource(nwidth, nheight,
ndata4, 0, nwidth));
}
else if (nbitcount == 1) {
// Have to determine the number of colors, the clrsused
// parameter is dominant if it is greater than zero. If
// zero1, calculate colors based on bitsperpixel.
int nNumColors = 0;
if (nclrused > 0) {
nNumColors = nclrused;
}
else {
nNumColors = (1 & 0xff) << nbitcount;
}
System.out.println("The number of Colors is" + nNumColors);

// Read the palatte colors.
int npalette[] = new int[nNumColors];
byte bpalette[] = new byte[nNumColors * 4];
fs.read(bpalette, 0, nNumColors * 4);
int nindex1 = 0;
for (int n = 0; n < nNumColors; n++) {
npalette
= (255 & 0xff) << 24
| ( ( (int) bpalette[nindex1 + 2] & 0xff) << 16)
| ( ( (int) bpalette[nindex1 + 1] & 0xff) << 8)
| (int) bpalette[nindex1] & 0xff;
nindex1 += 4;
}

// Scan line is padded with zeroes to be a multiple of four bytes
int scanLineSize = ( ( (nwidth * nbitcount) + 31) & ~31) >> 3;

int ndata1[] = new int[nwidth * nheight];
//byte bdata[] = new byte[ scanLineSize * nheight];
byte blinedata[] = new byte[scanLineSize];
//fs.read(bdata, 0, scanLineSize * nheight);
nindex1 = 0;
for (int j1 = 0; j1 < nheight; j1++) {
fs.read(blinedata, 0, scanLineSize);
nindex1 = 0;

for (int i1 = 0; i1 < nwidth; i1++) {

if (nwidth * (nheight - j1 - 1) + i1 > nwidth * nheight-1)
break;
if (nindex1 > scanLineSize * nheight - 1)
break;

for (int pixPerByte = 0; pixPerByte < 8; pixPerByte++)
{
int shift = 8 - pixPerByte - 1;
ndata1[nwidth * (nheight - j1 - 1) + i1] =
npalette[ ( (int) (blinedata[nindex1]>>shift) & 0x1)];
if (pixPerByte != 7)
{
i1++;
if (i1 >= nwidth)
break;
}
}

nindex1++;
}
}

image = Toolkit.getDefaultToolkit().createImage
(new MemoryImageSource(nwidth, nheight,
ndata1, 0, nwidth));
}
else {
System.out.println("Not a 32-bit, 24-bit, 16-bit, 8-bit, 4-bit and 1-bit Windows Bitmap, aborting...");
image = (Image)null;
}

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