Ability to store into BMP format

svitava/svitava.c

@@ -755,11 +755,66 @@ int ppm_write_ascii(unsigned int width, unsigned int height,
     return 0;
 }
 
+int bmp_write(unsigned int width, unsigned int height,
+              unsigned char *pixels, const char *file_name) {
+    unsigned char bmp_header[] = {   /* BMP header structure: */
+        0x42, 0x4d,                  /* magic number */
+        0x46, 0x00, 0x00, 0x00,      /* size of header=70 bytes */
+        0x00, 0x00,                  /* unused */
+        0x00, 0x00,                  /* unused */
+        0x36, 0x00, 0x00, 0x00,      /* 54 bytes - offset to data */
+        0x28, 0x00, 0x00, 0x00,      /* 40 bytes - bytes in DIB header */
+        0x00, 0x00, 0x00, 0x00,      /* width of bitmap */
+        0x00, 0x00, 0x00, 0x00,      /* height of bitmap */
+        0x01, 0x0,                   /* 1 pixel plane */
+        0x18, 0x00,                  /* 24 bpp */
+        0x00, 0x00, 0x00, 0x00,      /* no compression */
+        0x00, 0x00, 0x00, 0x00,      /* size of pixel array */
+        0x13, 0x0b, 0x00, 0x00,      /* 2835 pixels/meter */
+        0x13, 0x0b, 0x00, 0x00,      /* 2835 pixels/meter */
+        0x00, 0x00, 0x00, 0x00,      /* color palette */
+        0x00, 0x00, 0x00, 0x00,      /* important colors */
+    };
+    FILE *fout;
+    int x, y;
+
+    bmp_header[18] = width & 0xff;
+    bmp_header[19] = (width >> 8) & 0xff;
+    bmp_header[20] = (width >> 16) & 0xff;
+    bmp_header[21] = (width >> 24) & 0xff;
+    bmp_header[22] = height & 0xff;
+    bmp_header[23] = (height >> 8) & 0xff;
+    bmp_header[24] = (height >> 16) & 0xff;
+    bmp_header[25] = (height >> 24) & 0xff;
+
+    fout = fopen(file_name, "wb");
+    if (!fout) {
+        return 1;
+    }
+    fwrite(bmp_header, sizeof(bmp_header), 1, fout);
+
+    /* pixel array */
+    for (y = height - 1; y >= 0; y--) {
+        unsigned char *p = pixels + y * width * 4;
+        for (x = 0; x < width; x++) {
+            /* swap RGB */
+            fwrite(p+2, 1, 1, fout);
+            fwrite(p+1, 1, 1, fout);
+            fwrite(p, 1, 1, fout);
+            /* next pixel */
+            p+=4;
+        }
+    }
+    fclose(fout);
+    return 0;
+}
+
 int main(void) {
 #define WIDTH 256
 #define HEIGHT 256
     unsigned char *pixels = (unsigned char *)malloc(WIDTH * HEIGHT * 4);
     render_test_rgb_image(WIDTH, HEIGHT, pixels, 0);
     ppm_write_ascii(WIDTH, HEIGHT, pixels, "test_rgb_1.ppm");
+    bmp_write(WIDTH, HEIGHT, pixels, "test_rgb_1.bmp");
     return 0;
 }