From 0c1035bcc5a2c78640f45d0bd5f4454a51c87398 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Thu, 22 Apr 2021 11:05:41 +0200
Subject: Add support for output 1bpp packed sprites

---
 src/main.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 64 insertions(+), 14 deletions(-)

diff --git a/src/main.c b/src/main.c
index 54864cd..67c5d69 100644
--- a/src/main.c
+++ b/src/main.c
@@ -44,22 +44,64 @@ typedef struct Image {
     int n_channels;
 } Image;
 
+u8
+pack_1bb(u32 hex) {
+    u32 low_nibble = hex & 0xFFFF;
+    u32 high_nibble = (hex >> 16) & 0xFFFF;
+    u32 low = (low_nibble & 0x1);
+    low += 2 * ((low_nibble >> 4) & 0x1);
+    low += 4 * ((low_nibble >> 8) & 0x1);
+    low += 8 * ((low_nibble >> 12) & 0x1);
+    u32 high = (high_nibble & 0x1);
+    high += 2 * ((high_nibble >> 4) & 0x1);
+    high += 4 * ((high_nibble >> 8) & 0x1);
+    high += 8 * ((high_nibble >> 12) & 0x1);
+    return (high << 4) | low;
+}
+
 void
-export_c_file(Tiles *tiles, Palette *palette, FILE *file) {
+export_c_file(Tiles *tiles, Palette *palette, FILE *file, bool pack_1bpp) {
     // Output tiles.
-    fprintf(file, "u32 tiles[%lu][%u] = {\n", tiles->capacity, TILE_SIZE);
-    for (size_t i = 0; i < tiles->capacity; ++i) {
-        fprintf(file, "    {");
-        for (size_t j = 0; j < TILE_SIZE; ++j) {
-            fprintf(file, "0x%08x", tiles->data[i][j]);
-            if (j != (TILE_SIZE - 1)) {
-                fprintf(file, ", ");
+    if (pack_1bpp) {
+        fprintf(file, "u32 packed_tiles[] = {\n    ");
+        size_t counter = 0;
+        for (size_t i = 0; i < tiles->capacity; ++i) {
+            for (size_t j = 0; j < TILE_SIZE; j += 4, counter++) {
+                if (counter == 4) {
+                    counter = 0;
+                    fprintf(file, "\n    ");
+                }
+                u32 tile_a = tiles->data[i][j];
+                u32 tile_b = tiles->data[i][j + 1];
+                u32 tile_c = tiles->data[i][j + 2];
+                u32 tile_d = tiles->data[i][j + 3];
+                u32 packed = pack_1bb(tile_d);
+                packed |= pack_1bb(tile_c) << 8;
+                packed |= pack_1bb(tile_b) << 16;
+                packed |= pack_1bb(tile_a) << 24;
+                fprintf(file, "0x%08x,", packed);
+                if (counter < 3) {
+                    fprintf(file, " ");
+                }
             }
         }
-        fprintf(file, "},\n");
+        fprintf(file, "\n};\n");
+        fprintf(file, "\n");
+    } else {
+        fprintf(file, "u32 tiles[%lu][%u] = {\n", tiles->capacity, TILE_SIZE);
+        for (size_t i = 0; i < tiles->capacity; ++i) {
+            fprintf(file, "    {");
+            for (size_t j = 0; j < TILE_SIZE; ++j) {
+                fprintf(file, "0x%08x", tiles->data[i][j]);
+                if (j != (TILE_SIZE - 1)) {
+                    fprintf(file, ", ");
+                }
+            }
+            fprintf(file, "},\n");
+        }
+        fprintf(file, "};\n");
+        fprintf(file, "\n");
     }
-    fprintf(file, "};\n");
-    fprintf(file, "\n");
 
     // Output palette.
     fprintf(file, "u16 palette[%lu] = {\n", palette->capacity);
@@ -153,10 +195,13 @@ print_usage(void) {
     printf("\t-o <out_file.c>\tPath to the output file. If blank, stdout will be used.\n");
     printf("\t-W <8>\tSelect the sprite width in pixels. Must be a multiple of the tile size.\n");
     printf("\t-H <8>\tSelect the sprite height in pixels. Must be a multiple of the tile size.\n");
+    printf("\t-1\tBit pack the output to 1bbp (4x size reduction).\n");
     printf("\t-h\tShow help.\n");
     printf("\n");
 }
 
+// TODO: Enable 1bit bit-packing (in u32 units).
+// TODO: Support multiple files at once?
 int
 main(int argc, char *argv[]) {
     // Initialize default parameters.
@@ -165,9 +210,10 @@ main(int argc, char *argv[]) {
     size_t sprite_width = TILE_SIZE;
     size_t sprite_height = TILE_SIZE;
     char *out_file_path = NULL;
+    bool pack_1bpp = false;
 
     int option;
-    while ((option = getopt(argc, argv, "hb:o:W:H:")) != -1) {
+    while ((option = getopt(argc, argv, "hb:o:W:H:1")) != -1) {
         switch (option) {
             case 'b': {
                 // Background color.
@@ -226,6 +272,10 @@ main(int argc, char *argv[]) {
                 // Output file.
                 out_file_path = optarg;
             } break;
+            case '1': {
+                // Pack output to 1bpp.
+                pack_1bpp = true;
+            } break;
             case 'h': {
                 // Help.
                 print_usage();
@@ -302,14 +352,14 @@ main(int argc, char *argv[]) {
     }
 
     if (out_file_path == NULL) {
-        export_c_file(&tiles, &palette, stdout);
+        export_c_file(&tiles, &palette, stdout, pack_1bpp);
     } else {
         FILE *file = fopen(out_file_path, "w");
         if (!file) {
             fprintf(stderr, "%s: can't open output file: %s\n", BIN_NAME, out_file_path);
             return EXIT_FAILURE;
         }
-        export_c_file(&tiles, &palette, file);
+        export_c_file(&tiles, &palette, file, pack_1bpp);
         fclose(file);
     }
 
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