本文介绍了一个Java工具类，用于将Image对象转换为PNG格式的字节数据，包括处理图像颜色索引、生成PNG各段数据及进行必要的校验。
Image对象转成PNG格式字节 。没有做LZ77压。
共三个文件。
pngtools.java image转png格式工具类
bytestools.java byte操作类
crcutil crc校验类
转载请注明出处，可自由使用，无使用限，但商用请通知我。
pngtools.java
/** 
* @功能：image 生成 png 字节 * @作者: imuse * @MAIL: postzhu@hotmail.com * @blog: http://blog.youkuaiyun.com/imuse * @注 可自由使用，无使用限制。如商用请通知我
*/import javax.microedition.lcdui.Image;public class PngTools { public static final int BIT4 = 4; public static final int BIT8 = 8; 
/** PNG tag. */
private static final byte PNG[] = {-119, 80, 78, 71, 13, 10, 26, 10}; /** IHDR tag. */ private static final byte IHDR[] = {73, 72, 68, 82}; /** PLTE tag. */ private static final byte PLTE[] = {0x50,0x4C,0x54,0x45}; /** IDAT tag. */ private static final byte IDAT[] = {73, 68, 65, 84}; /** LZ77 tag. */ private static final byte LZ77[] = {0x78, (byte)0xDA, 0x01}; /** IEND tag. */ private static final byte IEND[] = {(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x49, (byte) 0x45, (byte) 0x4E, (byte) 0x44, (byte) 0xAE, (byte) 0x42, (byte) 0x60, (byte) 0x82}; /** * @功能 Image转成PNG字节 * @参数 Image srcImage 原图<br>int bit色深<br> * @返回值 转换后的图片
* */ public static byte[] imageToPng(Image srcImg, int bit){ int srcW = srcImg.getWidth(); int srcH = srcImg.getHeight(); int[] srcRGB = new int[srcW]; int[] nColorArr = new int[0]; //取出图片中所用到的所有颜色 for (int i = 0; i < srcH; i++) { //取一行颜色 srcImg.getRGB(srcRGB, 0, srcW, 0, i, srcW, 1); //取一行颜色中的不同值 int[] temp = GetColorArr(srcRGB); //将本行与上一次的结果连接 int[] count = new int[nColorArr.length+temp.length]; System.arraycopy(nColorArr, 0, count, 0, nColorArr.length); System.arraycopy(temp, 0, count, nColorArr.length, temp.length); //取连接后的结果再次取不同颜色 nColorArr = GetColorArr(count); } //如果没找到颜色则返回空 if(nColorArr.length==0){ return null; } int nPosCRC = 0; byte[] bRet; //固定头 bRet = BytesTools.appendBytes(null, PNG); //固定头长度 bRet = BytesTools.appendBytes(bRet, BytesTools.intToBytes(13)); nPosCRC = bRet.length; //IHDR bRet = BytesTools.appendBytes(bRet, IHDR); //宽 bRet = BytesTools.appendBytes(bRet, BytesTools.intToBytes(srcW)); //高 bRet = BytesTools.appendBytes(bRet, BytesTools.intToBytes(srcH)); //色深 bRet = BytesTools.appendBytes(bRet, (byte)bit); //颜色类型 bRet = BytesTools.appendBytes(bRet, 0x03); //规定此处总为0 bRet = BytesTools.appendBytes(bRet, 0x00); //同上 bRet = BytesTools.appendBytes(bRet, 0x00); //非隔行扫描 bRet = BytesTools.appendBytes(bRet, 0x00); //头信息CRC int nCRC = CRCUtil.checksum(bRet, nPosCRC, bRet.length-nPosCRC); bRet = BytesTools.appendBytes(bRet, BytesTools.intToBytes(nCRC)); //颜色总数 int nColorLen = nColorArr.length; bRet = BytesTools.appendBytes(bRet, BytesTools.intToBytes(nColorLen*3)); nPosCRC = bRet.length; //PLTE bRet = BytesTools.appendBytes(bRet, PLTE); for (int i = 0; i < nColorLen; i++) { bRet = BytesTools.appendBytes(bRet, intToRGBBytes(nColorArr[i])); } //CRC PLTE nCRC = CRCUtil.checksum(bRet, nPosCRC, bRet.length-nPosCRC); bRet = BytesTools.appendBytes(bRet, BytesTools.intToBytes(nCRC)); //IDTA长度 int nIdtaLen = 0; if(bit==BIT4){ nIdtaLen = (srcW/2+1)*srcH; }else if(bit==BIT8){ nIdtaLen = (srcW+1)*srcH; } int nLen = 4+LZ77.length+4+nIdtaLen; bRet = BytesTools.appendBytes(bRet, BytesTools.intToBytes(nLen)); nPosCRC = bRet.length; //IDAT bRet = BytesTools.appendBytes(bRet, IDAT); //无压缩的LZ77压缩块 bRet = BytesTools.appendBytes(bRet, LZ77); //长度 bRet = BytesTools.appendBytes(bRet, getIDATLen(nIdtaLen)); //数据区域 int nAl = bRet.length; if(bit==BIT4){ bRet = BytesTools.appendBytes(bRet, getPngBytes(srcImg, nColorArr)); }else if(bit==BIT8){ bRet = BytesTools.appendBytes(bRet, getPngBytes8(srcImg, nColorArr)); } //Adler32 bRet = BytesTools.appendBytes(bRet, Adler(bRet, nAl, bRet.length-nAl)); //CRC nCRC = CRCUtil.checksum(bRet, nPosCRC, bRet.length-nPosCRC); bRet = BytesTools.appendBytes(bRet, BytesTools.intToBytes(nCRC)); //IEND bRet = BytesTools.appendBytes(bRet, IEND); return bRet; } //Adler校验 private static byte[] Adler(byte[] bData, int nStart, int nLen){ int adler1=1; int adler2=0; nLen += nStart; for(int i=nStart;i<nLen;i++) { adler1=adler1+((int)bData[i]&0xff); adler2=adler1+adler2; adler1%=65521; adler2%=65521; } int nRet = (adler2<<16) | adler1 ; return BytesTools.intToBytes(nRet); } //8位色深IDAT数据 private static byte[] getPngBytes8(Image srcImg, int[] nColorArr){ int srcW = srcImg.getWidth(); int srcH = srcImg.getHeight(); int[] srcRGB = new int[srcW]; byte[] bRet = new byte[(srcW+1)*srcH]; int nPos = 0; for (int i = 0; i < srcH; i++) { srcImg.getRGB(srcRGB, 0, srcW, 0, i, srcW, 1); nPos = i; bRet[i*srcW+nPos] = 0; for (int j = 0; j < srcW; j++) { bRet[i*srcW+nPos+j+1] = (byte)(getColorIndex(srcRGB[j], nColorArr)&0xFF); } } return bRet; } //4位色深IDAT数据 private static byte[] getPngBytes(Image srcImg, int[] nColorArr){ int srcW = srcImg.getWidth(); int srcH = srcImg.getHeight(); int[] srcRGB = new int[srcW]; byte[] bRet = new byte[(srcW/2+1)*srcH]; int nPos = 0; for (int i = 0; i < srcH; i++) { srcImg.getRGB(srcRGB, 0, srcW, 0, i, srcW, 1); nPos = i; bRet[i*srcW/2+nPos] = 0; int nIndex = 0; for (int j = 0; j < srcW; j++) { if(j%2==1 && j!=0){ nIndex = nIndex | (getColorIndex(srcRGB[j], nColorArr)&0xFF); bRet[i*srcW/2+j/2+1+nPos] = (byte)nIndex; }else{ nIndex = (getColorIndex(srcRGB[j], nColorArr)&0xFF)<<4; } } } return bRet; } //取颜色索引 private static int getColorIndex(int nColor, int[] nColorArr){ int nLen = nColorArr.length; int nIndex = -1; for (int i = 0; i < nLen; i++) { if(nColor==nColorArr[i]){ nIndex = i; break; } } return nIndex; } //将一个int color转红绿蓝byte数组 private static byte[] intToRGBBytes(int nColor){ byte[] bColor = new byte[3]; //红 bColor[0] = (byte)(nColor>>16&0xFF); //绿 bColor[1] = (byte)(nColor>>8&0xFF); //蓝 bColor[2] = (byte)(nColor&0xFF); return bColor; } //IDAT数据的长度，格式为：前两字节为IDAT长度，低字节在前,后两字节为前两字节的^值. private static byte[] getIDATLen(int nLen){ byte[] bRet = new byte[4]; bRet[0] = (byte)(nLen & 0xFF); bRet[1] = (byte)(nLen >> 8 & 0xFF); bRet[2] = (byte)(bRet[0] ^ 0xFF); bRet[3] = (byte)(bRet[1] ^ 0xFF); return bRet; } //从一个int数据中取出不同的int值 private static int[] GetColorArr(int[] nArr){ int nLen = nArr.length; int nRet[] = new int[0]; for (int i = 0; i < nLen; i++) { int nrLen = nRet.length; boolean is = true; for (int j = 0; j < nrLen; j++) { if(nArr[i]==nRet[j]){ is = false; break; } } if(is){ int[] temp = new int[nrLen+1]; System.arraycopy(nRet, 0, temp, 0, nrLen); temp[nrLen] = nArr[i]; nRet = temp; } } return nRet; }}
bytestools.java
/** * @功能：字节工具类 * @作者: imuse * @MAIL: postzhu@hotmail.com * @blog: http://blog.youkuaiyun.com/imuse * @注 可自由使用，无使用限制。如商用请通知我 */public class BytesTools { /** * @功能: 将一个int值转为byte数组 * @参数: int nNum 要转的int值 * @返回值: byte[] bytesRet 转后的byte数组 */ public static byte[] intToBytes(int nNum) { byte[] bytesRet = new byte[4]; bytesRet[0] = (byte) ((nNum >> 24) & 0xFF); bytesRet[1] = (byte) ((nNum >> 16) & 0xFF); bytesRet[2] = (byte) ((nNum >> 8) & 0xFF); bytesRet[3] = (byte) (nNum & 0xFF); return bytesRet; } /** * @功能: 将一个长度为4 byte数组转为int * @参数: byte[] bNum要转的字节数组 * @返回值: int retInt 转后的int值 */ public static int bytesToInt(byte[] bNum) { return bytesToInt(bNum, 0); } /** * @功能: 将一个长度为4 byte数组转为int * @参数: byte[] bNum要转的字节数组<br>int nStartPos起始位置 * @返回值: int retInt 转后的int值 */ public static int bytesToInt(byte[] bNum, int nStartPos) { int retInt = 0; retInt = ((bNum[nStartPos++] & 0xFF) << 24); retInt += (bNum[nStartPos++] & 0xFF) << 16; retInt += (bNum[nStartPos++] & 0xFF) << 8; retInt += bNum[nStartPos] & 0xFF; return retInt; } /** * @功能: 将一个INT的转为byte数组后追加到指定数组后 * @参数: byte[] bDes追加目标<br>int bSrc要追加的int * @返回值: byte[] 追加后的字节数组 */ public static byte[] appendBytes(byte[] bDes, int bSrc) { return appendBytes(bDes, new byte[]{(byte)bSrc}); } /** * @功能: 将一个byte 数组追加到指定数组后 * @参数: byte[] bDes追加目标<br>byte[] bSrc要追加的字节数组 * @返回值: byte[] 追加后的字节数组 */ public static byte[] appendBytes(byte[] bDes, byte[] bSrc) { byte[] ret = null; if (bDes == null) { ret = bSrc; } if (bSrc == null) { ret = bDes; } if (bDes != null && bSrc != null) { ret = new byte[bDes.length + bSrc.length]; System.arraycopy(bDes, 0, ret, 0, bDes.length); System.arraycopy(bSrc, 0, ret, bDes.length, bSrc.length); } return ret; } /** * @功能: 截取指定byte 数组中的字节数组 * @参数: byte[] bSrc原字节数组<br>int nStartPos原字节数组起始位置<br>int nLen截取长度 * @返回值: byte[] 截取后的字节数组 */ public static byte[] subBytes(byte[] bSrc, int nStartPos, int nLen) { byte[] ret = null; if (bSrc != null) { ret = new byte[nLen]; if((nStartPos+nLen)<=bSrc.length){ System.arraycopy(bSrc, nStartPos, ret, 0, nLen); } } return ret; } /** * @功能: 查找子字节数组在父字节数组中的位置 * @参数: byte[] bSrc父字节数组<br>byte[] bSub子字节数组 * @返回值: int 在父字节数组中的位置，如未找到则返回-1 */ public static int findSubBytesPos(byte[] bSrc, byte[] bSub){ int ret = -1; int nSubLen = bSub.length; int nLen = bSrc.length-nSubLen; boolean b=true; for(int i=0; i<=nLen; i++){ b = true; for (int j = 0; j < nSubLen; j++) { if(bSrc[i+j]!=bSub[j]){ b = false; break; } } if(b){ ret = i; break; } } return ret; } }
crcutil.java
/** * @功能：CRC校验 * @作者: imuse * @MAIL: postzhu@hotmail.com * @blog: http://blog.youkuaiyun.com/imuse * @注 可自由使用，无使用限制。如商用请通知我 */public class CRCUtil { private static int[] crc_table; private static void make_crc_table() { int c; int n, k; crc_table = new int[256]; for (n = 0; n < 256; n++) { c = n; for (k = 0; k < 8; k++) { if ((c & 1) == 1) c = 0xedb88320 ^ (c >>> 1); else c = c >>> 1; } crc_table[n] = c; } } private static int update_crc(byte[] buf, int nStart, int nLen) { int c = 0xffffffff; int n; if (crc_table == null) { make_crc_table(); } for (n = nStart; n < nLen + nStart; n++) { c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >>> 8); } return c; } /** * @功能: 生成CRC校验码 * @参数: byte[] buf数据区域<br>int nStart起始位置<br>int nLen计算长度<br> * @返回值: int CRC校验码 * */ public static int checksum(byte[] buf, int nStart, int nLen) { return update_crc(buf, nStart, nLen) ^ 0xffffffff; } }
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