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#include <cstdio>
#include <cassert>
#include "bmp.h"
int64_t bmp_rgb_encoded_size(int width, int height) {
return 54 + (3 * (int64_t)width + 3) / 4 * 4 * (int64_t)height;
}
static void write_le32(uint8_t *dst, uint32_t value) {
dst[0] = value & 0xff;
dst[1] = (value >> 8) & 0xff;
dst[2] = (value >> 16) & 0xff;
dst[3] = value >> 24;
}
static void write_le16(uint8_t *dst, uint16_t value) {
dst[0] = value & 0xff;
dst[1] = value >> 8;
}
void bmp_rgb_encode_memory(uint8_t *dst, const uint8_t *src, int width, int height) {
const int64_t size = bmp_rgb_encoded_size(width, height);
const int padding = (4 - 3 * width % 4) % 4;
dst[0] = 'B';
dst[1] = 'M';
write_le32(&dst[2], size);
dst[6] = dst[7] = dst[8] = dst[9] = 0;
write_le32(&dst[10], 54);
write_le32(&dst[14], 40); // this is a BITMAPINFOHEADER
write_le32(&dst[18], width);
write_le32(&dst[22], height);
write_le16(&dst[26], 1);
write_le16(&dst[28], 24);
write_le32(&dst[30], 0);
write_le32(&dst[34], size - 54);
write_le32(&dst[38], 0); // pixels/metre; imagemagick sets this to 0
write_le32(&dst[42], 0); // and if they can, we can
write_le32(&dst[46], 0);
write_le32(&dst[50], 0);
int off = 54;
for (int y = height - 1; y >= 0; y--) {
for (int x = 0; x < width; x++) {
dst[off+0] = src[3 * (width * y + x) + 2];
dst[off+1] = src[3 * (width * y + x) + 1];
dst[off+2] = src[3 * (width * y + x) + 0];
off += 3;
}
for (int i = 0; i < padding; i++) dst[off++] = 0;
}
assert(off == size);
}
uint8_t* bmp_rgb_encode_memory_alloc(const uint8_t *src, int width, int height) {
const int64_t size = bmp_rgb_encoded_size(width, height);
uint8_t *dst = new uint8_t[size];
bmp_rgb_encode_memory(dst, src, width, height);
return dst;
}
void bmp_rgb_encode_file(const char *fname, const uint8_t *src, int width, int height) {
const int64_t size = bmp_rgb_encoded_size(width, height);
uint8_t *data = bmp_rgb_encode_memory_alloc(src, width, height);
FILE *f = fopen(fname, "w");
fwrite(data, 1, size, f);
fclose(f);
delete[] data;
}
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