From ba0fca599c1a06a0fc0f1d7089a1532be7f6454a Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Sat, 24 Apr 2021 18:50:03 +0200
Subject: Add support for x/y starting position and w/h for image size

---
 src/main.c | 49 +++++++++++++++++++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 12 deletions(-)

diff --git a/src/main.c b/src/main.c
index 67c5d69..f91ecd0 100644
--- a/src/main.c
+++ b/src/main.c
@@ -193,14 +193,16 @@ print_usage(void) {
     printf("\n");
     printf("\t-b <RRGGBB>\tSelects the background color used for transparency.\n");
     printf("\t-o <out_file.c>\tPath to the output file. If blank, stdout will be used.\n");
+    printf("\t-x <0>\tStart x position (in pixels).\n");
+    printf("\t-y <0>\tStart y position (in pixels).\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("\t-w <0>\tWidth of region to extract from (x0,y0). Defaults to image width.\n");
+    printf("\t-h <0>\tHeight of region to extract from (x0,y0). Defaults to image height.\n");
     printf("\n");
 }
 
-// TODO: Enable 1bit bit-packing (in u32 units).
 // TODO: Support multiple files at once?
 int
 main(int argc, char *argv[]) {
@@ -211,9 +213,13 @@ main(int argc, char *argv[]) {
     size_t sprite_height = TILE_SIZE;
     char *out_file_path = NULL;
     bool pack_1bpp = false;
+    size_t start_x = 0;
+    size_t start_y = 0;
+    size_t width = 0;
+    size_t height = 0;
 
     int option;
-    while ((option = getopt(argc, argv, "hb:o:W:H:1")) != -1) {
+    while ((option = getopt(argc, argv, "b:o:W:H:1x:y:w:h:")) != -1) {
         switch (option) {
             case 'b': {
                 // Background color.
@@ -276,10 +282,21 @@ main(int argc, char *argv[]) {
                 // Pack output to 1bpp.
                 pack_1bpp = true;
             } break;
+            case 'x': {
+                // Start x position in pixels.
+                start_x = atoi(optarg);
+            } break;
+            case 'y': {
+                // Start y position in pixels.
+                start_y = atoi(optarg);
+            } break;
+            case 'w': {
+                // Width of region to extract from (x0,y0).
+                width = atoi(optarg);
+            } break;
             case 'h': {
-                // Help.
-                print_usage();
-                return EXIT_SUCCESS;
+                // Height of region to extract from (x0,y0).
+                height = atoi(optarg);
             } break;
             default: {
                 print_usage();
@@ -323,8 +340,14 @@ main(int argc, char *argv[]) {
         return EXIT_FAILURE;
     }
 
-    size_t n_tiles_x = img.width / TILE_SIZE;
-    size_t n_tiles_y = img.height / TILE_SIZE;
+    if (width == 0) {
+        width = img.width;
+    }
+    if (height == 0) {
+        height = img.height;
+    }
+    size_t n_tiles_x = width / TILE_SIZE;
+    size_t n_tiles_y = height / TILE_SIZE;
     size_t n_tiles = n_tiles_x * n_tiles_y;
 
     // Allocate memory for the tiles in this file, with zero-initialization.
@@ -334,15 +357,17 @@ main(int argc, char *argv[]) {
         .capacity = n_tiles,
     };
 
-    size_t n_sprites_x = img.width / sprite_width;
-    size_t n_sprites_y = img.height / sprite_height;
+    int offset_x = start_x;
+    int offset_y = start_y;
+    size_t n_sprites_x = width / sprite_width;
+    size_t n_sprites_y = height / sprite_height;
     size_t n_sprite_tiles_x = sprite_width / TILE_SIZE;
     size_t n_sprite_tiles_y = sprite_height / TILE_SIZE;
     for (size_t p = 0; p < n_sprites_y; ++p) {
         for (size_t k = 0; k < n_sprites_x; ++k) {
             for (size_t j = 0; j < n_sprite_tiles_y; ++j) {
-                int offset_x = k * sprite_width;
-                int offset_y = p * sprite_height + j * TILE_SIZE;
+                int offset_x = start_x + k * sprite_width;
+                int offset_y = start_y + p * sprite_height + j * TILE_SIZE;
                 for (size_t i = 0; i < n_sprite_tiles_x; ++i) {
                     extract_tile(&tiles, &palette, &img, offset_x, offset_y);
                     offset_x += TILE_SIZE;
-- 
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