BMPError BMPLoad(std::string fname,BMPClass& bmp)
{
FILE * f=fopen(fname.c_str(),"rb"); //open for reading in binary mode
if(!f) return BMPNOOPEN;
char header[54];
fread(header,54,1,f); //read the 54bit main header
if(header[0]!='B' || header[1]!='M')
{
fclose(f);
return BMPNOTABITMAP; //all bitmaps should start "BM"
}
if(sizeof(int)==4) //Annoyingly I can't just assume this
{
bmp.width=*(int*)(header+18);
bmp.height=*(int*)(header+22);
}
else
{
bmp.width=header[18]+256*header[19]+256*256*header[20]+256*256*256*header[21];
bmp.height=header[22]+256*header[23]+256*256*header[24]+256*256*256*header[25];
}
bmp.allocateMem();
int bits=int(header[28]); //colourdepth
int x,y,c;
BYTE cols[256*4];
switch(bits)
{
case(24):
fread(bmp.bytes,bmp.width*bmp.height*3,1,f); //24bit is easy
for(x=0;x<bmp.width*bmp.height*3;x+=3) //except the format is BGR, grr
{
BYTE temp=bmp.bytes[x];
bmp.bytes[x]=bmp.bytes[x+2];
bmp.bytes[x+2]=temp;
}
break;
case(8):
fread(cols,256*4,1,f); //read colortable
for(y=0;y<bmp.height;++y) //(Notice 4bytes/col for some reason)
for(x=0;x<bmp.width;++x)
{
BYTE byte;
fread(&byte,1,1,f); //just read byte
for(int c=0;c<3;++c)
bmp.pixel(x,y,c)=cols[byte*4+2-c]; //and look up in the table
}
break;
case(4):
fread(cols,16*4,1,f);
for(y=0;y<256;++y)
for(x=0;x<256;x+=2)
{
BYTE byte;
fread(&byte,1,1,f); //as above, but need to exract two
for(c=0;c<3;++c) //pixels from each byte
bmp.pixel(x,y,c)=cols[byte/16*4+2-c];
for(c=0;c<3;++c)
bmp.pixel(x+1,y,c)=cols[byte%16*4+2-c];
}
break;
//NOT CURRENTLY WORKING PROPERLY
//case(1):
// fread(cols,8,1,f); //colourtable
// for(y=0;y<256;++y)
// for(x=0;x<256;x+=8)
// {
// BYTE byte;
// fread(&byte,1,1,f);
// //The idea here is that every byte is eight pixels
// //so I'm shifting the byte to the relevant position, then masking out
// //all but the lowest bit in order to get the index into the colourtable.
// for(int x2=0;x2<8;++x2)
// {
// for(int c=0;c<3;++c)
// bmp.pixel(x+x2,y,c)=cols[((byte>>(7-x2))&1)*4+2-c];
// }
// }
// break;
default:
fclose(f);
return BMPUNKNOWNFORMAT;
}
fclose(f);
if(ferror(f)) return BMPFILEERROR;
return BMPNOERROR;
}
BMPError BMPLoad(std::string fname,BMPClass& bmp)
{
if(sizeof(int)!=4) return BMPBADINT;
FILE* f=fopen(fname.c_str(),"rb"); //open for reading in binary mode
if(!f) return BMPNOOPEN;
char header[54];
fread(header,54,1,f); //read the 54bit main header
if(header[0]!='B' || header[1]!='M')
{
fclose(f);
return BMPNOTABITMAP; //all bitmaps should start "BM"
}
//it seems gimp sometimes makes its headers small, so we have to do this. hence all the fseeks
int offset=*(unsigned int*)(header+10);
bmp.width=*(int*)(header+18);
bmp.height=*(int*)(header+22);
//now the bitmap knows how big it is it can allocate its memory
bmp.allocateMem();
int bits=int(header[28]); //colourdepth
int x,y,c;
BYTE cols[256*4]; //colourtable
switch(bits)
{
case(24):
fseek(f,offset,SEEK_SET);
fread(bmp.bytes,bmp.width*bmp.height*3,1,f); //24bit is easy
for(x=0;x<bmp.width*bmp.height*3;x+=3) //except the format is BGR, grr
{
BYTE temp=bmp.bytes[x];
bmp.bytes[x]=bmp.bytes[x+2];
bmp.bytes[x+2]=temp;
}
break;
case(8):
fread(cols,256*4,1,f); //read colortable
fseek(f,offset,SEEK_SET);
for(y=0;y<bmp.height;++y) //(Notice 4bytes/col for some reason)
for(x=0;x<bmp.width;++x)
{
BYTE byte;
fread(&byte,1,1,f); //just read byte
for(int c=0;c<3;++c)
bmp.pixel(x,y,c)=cols[byte*4+2-c]; //and look up in the table
}
break;
case(4):
fread(cols,16*4,1,f);
fseek(f,offset,SEEK_SET);
for(y=0;y<256;++y)
for(x=0;x<256;x+=2)
{
BYTE byte;
fread(&byte,1,1,f); //as above, but need to exract two
for(c=0;c<3;++c) //pixels from each byte
bmp.pixel(x,y,c)=cols[byte/16*4+2-c];
for(c=0;c<3;++c)
bmp.pixel(x+1,y,c)=cols[byte%16*4+2-c];
}
break;
case(1):
fread(cols,8,1,f);
fseek(f,offset,SEEK_SET);
for(y=0;y<bmp.height;++y)
for(x=0;x<bmp.width;x+=8)
{
BYTE byte;
fread(&byte,1,1,f);
//Every byte is eight pixels
//so I'm shifting the byte to the relevant position, then masking out
//all but the lowest bit in order to get the index into the colourtable.
for(int x2=0;x2<8;++x2)
for(int c=0;c<3;++c)
bmp.pixel(x+x2,y,c)=cols[((byte>>(7-x2))&1)*4+2-c];
}
break;
default:
fclose(f);
return BMPUNKNOWNFORMAT;
}
if(ferror(f))
{
fclose(f);
return BMPFILEERROR;
}
fclose(f);
return BMPNOERROR;
}