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compress.cpp
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compress.cpp
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#include<stdio.h>
#include<string.h>
unsigned int GetCrc32(unsigned char* InStr,unsigned int len){
unsigned int Crc32Table[256];
unsigned int i,j;
unsigned int Crc;
for (i = 0; i < 256; i++){
Crc = i;
for (j = 0; j < 8; j++){
if (Crc & 1)
Crc = (Crc >> 1) ^ 0xEDB88320;
else
Crc >>= 1;
}
Crc32Table[i] = Crc;
}
Crc=0xffffffff;
for(unsigned int m=0; m<len; m++){
Crc = (Crc >> 8) ^ Crc32Table[(Crc & 0xFF) ^ InStr[m]];
}
Crc ^= 0xFFFFFFFF;
return Crc;
}
int main(int argc, char* argv[])
{
FILE *fp,*fpnew;
unsigned char *buf=NULL;
unsigned int len=0;
unsigned int ChunkLen=0;
unsigned int ChunkCRC32=0;
unsigned int ChunkOffset=0;
unsigned int crc32=0;
unsigned int i=0,j=0;
unsigned char Signature[8]={0x89,0x50,0x4e,0x47,0x0d,0x0a,0x1a,0x0a};
unsigned char IEND[12]={0x00,0x00,0x00,0x00,0x49,0x45,0x4e,0x44,0xae,0x42,0x60,0x82};
if((fp=fopen("c:\\test\\0.png","rb+"))==NULL)
return 0;
if((fpnew=fopen("c:\\test\\new.png","wb"))==NULL)
return 0;
fseek(fp,0,SEEK_END);
len=ftell(fp);
buf=new unsigned char[len];
fseek(fp,0,SEEK_SET);
fread(buf,len,1,fp);
printf("Total Len=%d\n",len);
printf("----------------------------------------------------\n");
fseek(fp,8,SEEK_SET);
ChunkOffset=8;
i=0;
fwrite(Signature,8,1,fpnew);
while(1)
{
i++;
j=0;
memset(buf,0,len);
fread(buf,4,1,fp);
fwrite(buf,4,1,fpnew);
ChunkLen=(buf[0]<<24)|(buf[1]<<16)|(buf[2]<<8)|buf[3];
fread(buf,4+ChunkLen,1,fp);
printf("[+]ChunkName:%c%c%c%c ",buf[0],buf[1],buf[2],buf[3]);
if(strncmp((char *)buf,"IHDR",4)==0|strncmp((char *)buf,"PLTE",4)==0|strncmp((char *)buf,"IDAT",4)==0)
{
printf("Palette Chunk\n");
fwrite(buf,4+ChunkLen,1,fpnew);
}
else
{
printf("Ancillary Chunk\n");
fseek(fpnew,-4,SEEK_CUR);
j=1;
}
printf(" ChunkOffset:0x%08x \n",ChunkOffset);
printf(" ChunkLen: %10d \n",ChunkLen);
crc32=GetCrc32(buf,ChunkLen+4);
printf(" ExpectCRC32:%08X\n",crc32);
fread(buf,4,1,fp);
ChunkCRC32=(buf[0]<<24)|(buf[1]<<16)|(buf[2]<<8)|buf[3];
printf(" ChunkCRC32: %08X ",ChunkCRC32);
if(crc32!=ChunkCRC32)
printf("[!]CRC32Check Error!\n");
else
{
printf("Check Success!\n\n");
if(j==0)
fwrite(buf,4,1,fpnew);
}
ChunkLen=ftell(fp);
if(ChunkLen==(len-12))
{
printf("\n----------------------------------------------------\n");
printf("Total Chunk:%d\n",i);
break;
}
}
fwrite(IEND,12,1,fpnew);
fclose(fp);
fclose(fpnew);
return 0;
}