Re: Common letters in the Alphabet.
Simon Wood wrote:
>
> For ELKSibo I have had to include a font bit map (as I have to draw each
> character to the LCD), this only has a few of the 255 ASCII codes and is the
> form:
> ASCII Value, data, data, data, etc,
>
> The renderer compares the first byte with it's desired character and moves
> to the next character should they not match.
>
> I would like to sequence the data so that the most common characters are
> near the start of the list and therefore speed up the display driver
> (believe me every little bit helps).
>
> Does anyone have letter probability table I could use??? (or any idea how to
> generate one)
>
> Simon Wood
>
How about something like this? The code should be small and fast,
and the data would be bigger only by the number of holes between
MIN_FONT_CHAR and MAX_FONT_CHAR.
#define MIN_FONT_CHAR 0x20 /* ? */
#define MAX_FONT_CHAR 0x7e /* ? */
#define N_CHAR (MAX_FONT_CHAR - MIN_FONT_CHAR + 1)
#define UNPRINTABLE N_CHAR
#define BYTES_PER_GLYPH 8/* ? */
static unsigned char lookup_index[N_CHAR] = {
0, 1, UNPRINTABLE, 2, UNPRINTABLE, /* ... */
};
static unsigned char font_data[N_CHAR + 1][BYTES_PER_GLYPH] = {
{0,0,0,0,0,0,0,0},/* data for MIN_FONT_CHAR */
{0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0},
/* ... */
{0,0,0,0,0,0,0,0},/* data for MAX_FONT_CHAR */
{0,0,0,0,0,0,0,0} /* data for UNPRINTABLE char */
};
unsigned char *get_font_data(unsigned char c) {
if (c < MIN_FONT_CHAR || c > MAX_FONT_CHAR) {
return font_data[UNPRINTABLE];
}
return font_data[lookup_index[c - MIN_FONT_CHAR]];
}
Re: Common letters in the Alphabet.
Simon Wood wrote: > > For ELKSibo I have had to include a font bit map (as I have to draw each > character to the LCD), this only has a few of the 255 ASCII codes and is the > form: > ASCII Value, data, data, data, etc, > > The renderer compares the first byte with it's desired character and moves > to the next character should they not match. > > I would like to sequence the data so that the most common characters are > near the start of the list and therefore speed up the display driver > (believe me every little bit helps). > > Does anyone have letter probability table I could use??? (or any idea how to > generate one) Letter probability is closely related to the letter typed earlier. Maybe it's an idea to enlarge the size of you fint bit map struct and store after each character a pointer to the character most likely to follow it. The probability table could be easily found by simply downloading a few books in the language of your choice and have a script count letters and correlations between letters. Furthermore I don't quite understand why you choose to step through the font bit map structure. If you have stored it as an array, isn't it simpler to simply use the ascii code as a memory index. This would only require you to place the array at a smart location (for instance at the beginning of some segment or an integer number of pages from it) so that you can avoid having to do multiplications when calculating the memory adress. If you fix it in such a way that each entry in the array is some power of 2 bytes long, you can calcuted the memory adress from the index by doing a shift and an add. Correct me if this is a stupid idea, I'm ne wat this. > > Simon Wood Dries
Common letters in the Alphabet.
For ELKSibo I have had to include a font bit map (as I have to draw each character to the LCD), this only has a few of the 255 ASCII codes and is the form: ASCII Value, data, data, data, etc, The renderer compares the first byte with it's desired character and moves to the next character should they not match. I would like to sequence the data so that the most common characters are near the start of the list and therefore speed up the display driver (believe me every little bit helps). Does anyone have letter probability table I could use??? (or any idea how to generate one) Simon Wood Hardware Engineer Pace Micro Technology plc Victoria Road, Saltaire, Shipley West Yorkshire, BD18 3LF Tel : +44(0)1274 532000 Fax: +44(0)1274 532029 This E-Mail and any attachments hereto are strictly confidential and intended solely for the addressee. If you are not the intended addressee please notify the sender by return and delete the message. You must not disclose, forward or copy this E-mail or attachments to any third party without the prior consent of the sender.
