修改png图的调色板
今天在硬盘上挖出这个存放了几年的代码。又回忆起3年前的那个j2me手机游戏程序员……这个算法是参考一位高人的文章，直接读取并修改png格式图片的调色板，然后生成新的调色板替代原来的。
这样可以实现游戏中常见的变色效果，可以解决游戏容量有限，不能存放太多精灵图片的问题。
具体过程其实并不复杂，大家可以先搜索资料，先看看png图片的格式定义。这个算法正是找到调色板区，根据原有格式修改之后，生成新的crc校验码，然后替换原来的调色板。这样就可以用一个png图片，创建多个变色副本。
<div style="border: 1px solid #cccccc; padding: 4px 5px 4px 4px; background-color: #eeeeee; font-size: 13px; width: 98%;"><!---->public class PalettedImage {
public Image getPalettedImage(byte[] data, int[] originalColors,
int[] palettedColors) {
byte[] tempData = new byte;
System.arraycopy(data, 0, tempData, 0, data.length);
Image img = null;
int[] parameter = { 0, 0, 0 };
analyze(tempData, parameter);
for (int i = 0; i < originalColors.length; i++) {
replaceColor(tempData, parameter, originalColors,
palettedColors);
}
fillData(tempData, parameter);
try {
img = Image.createImage(tempData, 0, data.length);
} catch (Exception e) {
System.out.println("getPalettedImage && " + e.toString());
}
return img;
}
private void analyze(byte[] data, int[] para) {
int offset = 8;
int chunkLen = 0;
while (data+ 4] != 0x50 || data+ 5] != 0x4c
|| data+ 6] != 0x54 || data+ 7] != 0x45) {
chunkLen = readInt(data, offset);
offset += (4 + 4 + chunkLen + 4);
}
chunkLen = readInt(data, offset);
para[2] = chunkLen / 3;
para[0] = offset + 8;
para[1] = offset + 8 + chunkLen;
}
private int readInt(byte[] data, int offset) {
return ((data & 0xFF) << 24)
| ((data+ 1] & 0xFF) << 16)
| ((data+ 2] & 0xFF) << 8) | (data+ 3] & 0xFF);
}
private void replaceColor(byte[] data, int[] para, int oldColor,
int newColor) {
byte rr = (byte) ((oldColor >> 16) & 0xff);
byte gg = (byte) ((oldColor >> 8) & 0xff);
byte bb = (byte) (oldColor & 0xff);
for (int i = 0, offset = para[0], temp = 0; i < para[2]; i++, offset += 3) {
if (rr == data && gg == data+ 1]
&& bb == data+ 2]) {
data = (byte) ((newColor >> 16) & 0xff);
data+ 1] = (byte) ((newColor >> 8) & 0xff);
data+ 2] = (byte) (newColor & 0xff);
break;
}
}
}
private void fillData(byte[] data, int[] para) {
int checksum = update_crc(data, para[0] - 4, para[2] * 3 + 4);
data1]] = (byte) ((checksum >> 24) & 0xff);
data1] + 1] = (byte) ((checksum >> 16) & 0xff);
data1] + 2] = (byte) ((checksum >> 8) & 0xff);
data1] + 3] = (byte) ((checksum) & 0xff);
}
private int update_crc(byte[] buf, int off, int len) {
int c = 0xffffffff;
int n, k;
int xx;
int[] crc_table = new int[256];
for (n = 0; n < 256; n++) {
xx = n;
for (k = 0; k < 8; k++) {
if ((xx & 1) == 1) {
xx = 0xedb88320 ^ (xx >>> 1);
} else {
xx = xx >>> 1;
}
}
crc_table = xx;
}
for (n = off; n < len + off; n++) {
c = crc_table[(c ^ buf) & 0xff] ^ (c >>> 8);
}
return (c ^ 0xffffffff);
}
}
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