Question

I have a C header file that contains 10×12 pixel bitmap font characters in an array of 2×12 (for a mono color lcd). This wastes the lower 6-bits of every other byte, not to mention being harder to render for having to skip the paddings.

What is the easiest way to convert this to simple serialized bits without the padded bits?

the solution that I see has a lot of complicated bit banging. Is there an easy way to do perform this?

0x00,0x00,  /*  ................  */
0x30,0x00,  /*  ..@@............  */
0x78,0x00,  /*  .@@@@...........  */
0x48,0x00,  /*  .@..@...........  */
0xCC,0x00,  /*  @@..@@..........  */
0xCC,0x00,  /*  @@..@@..........  */
0xCC,0x00,  /*  @@..@@..........  */
0xFC,0x00,  /*  @@@@@@..........  */
0xCC,0x00,  /*  @@..@@..........  */
0xCC,0x00,  /*  @@..@@..........  */
0x00,0x00,  /*  ................  */
0x00,0x00   /*  ................  */

Answer 1

A simplified version can create a producer consumer going one bit at a time which keeps the bit banging to a sane level. Here’s what I ended up doing:

#define CHAR_W 10
#define CHAR_H 12
#define NUM_CHARS 100
#define CEILING(x,y) (((x) + (y) - 1) / (y))
#define BYTES CEILING(CHAR_W, 8)
#define BIT(x, n) ( ((1 << n) & x) >> n )
#define COPYBIT(b,x,n) (((0x1 & b) << n) | x)
#define CHAR_BYTES CEILING(CHAR_H * CHAR_W, 8)
#define OUTBYTES NUM_CHARS * CHAR_BYTES

int main()
{
    int totinbit = 0;
    int locinbit = 0;
    int locoutbit = 7;  // start with msb 
    int totoutbit = 0;
    int bytes = BYTES;

    unsigned char c = 0;
    unsigned char o = 0;
    unsigned char buf[OUTBYTES];

    while (totoutbit < NUM_CHARS * CHAR_H * CHAR_W)
    {
        c = fontArray[totinbit / 8];
        locinbit = 7 - totinbit % 8;

        o = COPYBIT(BIT(c,locinbit),o,locoutbit);

        // reset out counter, full byte produced
        if (--locoutbit < 0)
        {
            locoutbit = 7;
            buf[totoutbit  / 8] = o;
            o = 0;
        }

        // skip over the padding bits
        if ((totoutbit % CHAR_W) == (CHAR_W - 1))
            totinbit =  CEILING(totinbit,8) * 8 - 1;

        totinbit++;     
        // character boundary
        if ( (totinbit % (bytes * 8 * CHAR_H)) == 0 && totinbit > 0)
        {
                            // pad the last byte in the character if necessary
            if (locoutbit != 7)
                    locoutbit = 7;
        }

        totoutbit++;


        }
 // at this point buf contains the converted bitmap array
}