Jsummers: Category:Booting

2017-08-15T14:47:55Z

Category:Booting

Felix: Created page with "{{FormatInfo | subcat = Graphics }} '''GLE''' is a simple monochrome graphics format used for storing the Energy Star logo in AMI BIOS images. Full splash screens are usu..."

2015-03-09T08:44:42Z

Created page with "{{FormatInfo | subcat = Graphics }} '''GLE''' is a simple monochrome graphics format used for storing the Energy Star logo in AMI BIOS images. Full splash screens are usu..."

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{{FormatInfo
| subcat = Graphics
}}
'''GLE''' is a simple monochrome graphics format used for storing the Energy Star logo in AMI [[BIOS]] images. Full splash screens are usually stored in the [[PCX]] format.

== Structure ==
The layout of a GLE file is as follows.
{| class="wikitable"
! Name
! Length
! Description
|-
| magic
| 3 bytes
| Always contains <code>'G' 'L' 'E'</code>, i.e. <code>47 4c 45</code>.
|-
| ???
| 1 byte
| Always equal to 1 in files known to this author. It is unknown whether it should be considered a part of the magic number, format version number, bit depth, set of flags or some other indicator.
|-
| width
| 1 byte
| Image width, in character cells; usually 11. One cell is 8 pixels wide.
|-
| height
| 1 byte
| Image height, in character cells; usually 3. One cell is 14 pixels high.
|-
| fgcolor
| 1 byte
| CGA colour number of foreground (1) pixels; usually 10 (light green). See [[wikipedia:Color Graphics Adapter#Color palette]].
|-
| bgcolor
| 1 byte
| CGA colour number of background (0) pixels; usually 0.
|-
| data
| ''width'' × ''height'' × 14 bytes
| The image data itself. The pixel data is stored in a way identical to the [[Award BIOS logo|EPAv1 format]]: character cell by character cell, left to right, top to bottom. Each character cell occupies 14 bytes: the first byte corresponds to the first row of the cell, and the most significant bit corresponds to the leftmost pixel.
|}

== Converter ==
The following C99 program converts a GLE image to [[XPM]].

<pre>
#include <stdio.h>
#include <stdint.h>
#include <errno.h>

struct gle_header {
char magic[3];
uint8_t reserved; /* = 1 */
uint8_t width;
uint8_t height;
uint8_t fgcolor;
uint8_t bgcolor;
};

static const uint_least32_t cga_palette[16] = {
0x000000, 0x0000aa, 0x00aa00, 0x00aaaa,
0xaa0000, 0xaa00aa, 0xaa5500, 0xaaaaaa,
0x555555, 0x5555ff, 0x55ff55, 0x55ffff,
0xff5555, 0xff55ff, 0xffff55, 0xffffff,
};

int main(int argc, char *argv[]) {
if (!argv[1]) {
fprintf(stderr, "usage: %s $filename\n", argv[0]);
return 1;
}

FILE *inf = fopen(argv[1], "rb");

struct gle_header header;
char magic[3];
if (!fread(&header, sizeof(header), 1, inf)) {
if (feof(inf))
fprintf(stderr, "%s: %s: cannot read header: premature end of file\n", argv[0], argv[1]);
else
fprintf(stderr, "%s: %s: cannot read header: %s [%d]\n", argv[0], argv[1], strerror(errno), errno);
return 1;
}
if (memcmp(header.magic, "GLE", 3)) {
fprintf(stderr, "%s: %s: magic number mismatch\n", argv[0], argv[1]);
return 1;
}

if (header.reserved != 1) {
fprintf(stderr, "%s: %s: reserved byte == %u (!= 1), conversion may fail\n", argv[0], argv[1], header.reserved);
}

uint8_t bitmap[header.width * header.height * 14];
if (!fread(bitmap, sizeof(bitmap), 1, inf)) {
if (feof(inf))
fprintf(stderr, "%s: %s: cannot read bitmap data: premature end of file\n", argv[0], argv[1]);
else
fprintf(stderr, "%s: %s: cannot read bitmap data: %s [%d]\n", argv[0], argv[1], strerror(errno), errno);
return 1;
}

printf("/* XPM */\n");
printf("static char *gle[] = {\n");
printf("\"%u %u 2 1 \",\n", header.width * 8, header.height * 14);
printf("\" c #%06x\",\n", cga_palette[header.bgcolor]);
printf("\"@ c #%06x\",\n", cga_palette[header.fgcolor]);

for (size_t y = 0; y < 14 * header.height; ++y) {
printf("\"");
for (size_t x = 0; x < header.width; ++x) {
uint8_t b = bitmap[(y - y % 14) * header.width + 14 * x + (y % 14)];
printf("%c%c%c%c%c%c%c%c",
(b >> 7) ? '@' : ' ',
(b >> 6) & 1 ? '@' : ' ',
(b >> 5) & 1 ? '@' : ' ',
(b >> 4) & 1 ? '@' : ' ',
(b >> 3) & 1 ? '@' : ' ',
(b >> 2) & 1 ? '@' : ' ',
(b >> 1) & 1 ? '@' : ' ',
(b ) & 1 ? '@' : ' '
);
}
printf("\",\n");
}

printf("};\n");

return 0;
}
</pre>

← Older revision		Revision as of 14:47, 15 August 2017
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GLE - Revision history

Jsummers: Category:Booting

Felix: Created page with "{{FormatInfo | subcat = Graphics }} '''GLE''' is a simple monochrome graphics format used for storing the Energy Star logo in AMI BIOS images. Full splash screens are usu..."