128 lines
3.5 KiB
C
128 lines
3.5 KiB
C
// bmp2raw.c -- Convert a 320x200x256 BMP to raw VGA splash format
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//
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// Output format:
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// 768 bytes: palette (256 x 3 bytes RGB, 6-bit VGA values)
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// 64000 bytes: pixels (320x200, top-to-bottom scanline order)
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//
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// Total output: 64768 bytes
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#define VGA_W 320
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#define VGA_H 200
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#define PALETTE_ENTRIES 256
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#define PIXEL_COUNT (VGA_W * VGA_H)
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int main(int argc, char **argv) {
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if (argc != 3) {
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fprintf(stderr, "Usage: bmp2raw <input.bmp> <output.raw>\n");
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return 1;
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}
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FILE *fp = fopen(argv[1], "rb");
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if (!fp) {
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fprintf(stderr, "Cannot open %s\n", argv[1]);
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return 1;
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}
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// Read BMP header
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uint8_t hdr[54];
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if (fread(hdr, 1, 54, fp) != 54) {
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fprintf(stderr, "Bad BMP header\n");
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fclose(fp);
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return 1;
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}
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if (hdr[0] != 'B' || hdr[1] != 'M') {
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fprintf(stderr, "Not a BMP file\n");
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fclose(fp);
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return 1;
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}
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uint32_t pixelOffset = hdr[10] | (hdr[11] << 8) | (hdr[12] << 16) | (hdr[13] << 24);
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int32_t width = hdr[18] | (hdr[19] << 8) | (hdr[20] << 16) | (hdr[21] << 24);
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int32_t height = hdr[22] | (hdr[23] << 8) | (hdr[24] << 16) | (hdr[25] << 24);
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uint16_t bpp = hdr[28] | (hdr[29] << 8);
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if (width != VGA_W || abs(height) != VGA_H || bpp != 8) {
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fprintf(stderr, "BMP must be %dx%d 8bpp (got %dx%d %dbpp)\n", VGA_W, VGA_H, width, abs(height), bpp);
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fclose(fp);
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return 1;
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}
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bool topDown = (height < 0);
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if (height < 0) {
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height = -height;
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}
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// Read palette (starts at offset 54 for BITMAPINFOHEADER, may vary)
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uint32_t dibSize = hdr[14] | (hdr[15] << 8) | (hdr[16] << 16) | (hdr[17] << 24);
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uint32_t palOffset = 14 + dibSize; // BMP file header (14) + DIB header
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fseek(fp, palOffset, SEEK_SET);
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uint8_t bmpPal[PALETTE_ENTRIES * 4];
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if (fread(bmpPal, 4, PALETTE_ENTRIES, fp) != PALETTE_ENTRIES) {
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fprintf(stderr, "Cannot read palette\n");
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fclose(fp);
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return 1;
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}
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// Convert palette: BMP is BGRA 8-bit, VGA is RGB 6-bit
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uint8_t vgaPal[PALETTE_ENTRIES * 3];
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for (int i = 0; i < PALETTE_ENTRIES; i++) {
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vgaPal[i * 3 + 0] = bmpPal[i * 4 + 2] >> 2; // R
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vgaPal[i * 3 + 1] = bmpPal[i * 4 + 1] >> 2; // G
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vgaPal[i * 3 + 2] = bmpPal[i * 4 + 0] >> 2; // B
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}
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// Read pixel data
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fseek(fp, pixelOffset, SEEK_SET);
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// BMP rows are padded to 4-byte boundaries (320 is already aligned)
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uint8_t pixels[PIXEL_COUNT];
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if (topDown) {
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// Already top-to-bottom
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if (fread(pixels, 1, PIXEL_COUNT, fp) != PIXEL_COUNT) {
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fprintf(stderr, "Cannot read pixel data\n");
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fclose(fp);
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return 1;
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}
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} else {
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// Bottom-to-top — flip
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for (int y = VGA_H - 1; y >= 0; y--) {
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if (fread(pixels + y * VGA_W, 1, VGA_W, fp) != VGA_W) {
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fprintf(stderr, "Cannot read row %d\n", VGA_H - 1 - y);
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fclose(fp);
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return 1;
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}
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}
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}
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fclose(fp);
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// Write output
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FILE *out = fopen(argv[2], "wb");
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if (!out) {
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fprintf(stderr, "Cannot create %s\n", argv[2]);
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return 1;
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}
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fwrite(vgaPal, 1, sizeof(vgaPal), out);
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fwrite(pixels, 1, PIXEL_COUNT, out);
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fclose(out);
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printf("Converted %s -> %s (%d bytes)\n", argv[1], argv[2], (int)(sizeof(vgaPal) + PIXEL_COUNT));
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return 0;
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}
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