54 lines
1.4 KiB
C
54 lines
1.4 KiB
C
#include <stdio.h>
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#include <sys/types.h>
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#include "bmp.h"
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#include "vesa.h"
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int readBMPHeader(FILE *fh, struct BMPImage *info) {
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int sizeOfHeader;
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char value;
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unsigned int numberOfUsedColors;
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if ((fgetc(fh) != 'B') || (fgetc(fh) != 'M')) {
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printf("Not a BMP file\n");
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return 1;
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}
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fseek(fh, 12, SEEK_CUR);
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fread(&sizeOfHeader, sizeof(int), 1, fh);
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fread(&info->width, sizeof(int), 1, fh);
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fread(&info->height, sizeof(int), 1, fh);
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fseek(fh, 2, SEEK_CUR);
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fread(&info->bpp, sizeof(int), 1, fh);
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// for gimp, you need to add colors to the color map until it hits
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// 16 colors, then the image will be a 256 color, 8 bpp image
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//
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// https://www.gimp-forum.net/Thread-indexing-into-8-bit?pid=13233#pid13233
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if (info->bpp != 8) return 1;
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fseek(fh, 18, SEEK_CUR);
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fread(&numberOfUsedColors, sizeof(unsigned int), 1, fh);
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printf("used colors: %d\n",numberOfUsedColors);
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if (numberOfUsedColors > 256) return 1;
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// get down to color data
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fseek(fh, 14 + sizeOfHeader, SEEK_SET);
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fread(info->colors, sizeof(struct BMPColor), numberOfUsedColors, fh);
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return 0;
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}
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void bmp256ColorPaletteToVESAColorPalette(struct BMPImage* bmpImage, struct VESAColor colors[]) {
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int i;
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for (i = 0; i < 256; ++i) {
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colors[i].red = bmpImage->colors[i].red >> 2;
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colors[i].green = bmpImage->colors[i].green >> 2;
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colors[i].blue = bmpImage->colors[i].blue >> 2;
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}
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}
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