256-colors palette is now pre-computed on start

That kinda fixes weird issue with vertical stripes

Makefile

@@ -2,7 +2,7 @@ CFLAGS := -Wall -Wextra -Werror -pedantic -std=c99 -ggdb
 CLIBS := -lm
 INCLUDES := -Isrc
 OBJECTS := obj/stb_image.o obj/stb_image_resize.o \
-					 obj/colors.o obj/args.o obj/image.o \
+					 obj/colors.o obj/args.o obj/image.o obj/commons.o \
 					 obj/mod_blocks.o
 
 all: lib asciify

src/args.c

@@ -1,4 +1,5 @@
 #include "args.h"
+#include "colors.h"
 #include <getopt.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -242,6 +243,9 @@ int prepare_state(int argc, char **argv, asc_args_t args, asc_state_t *state)
     fclose(fp);
   }
   
+  if (args.out_style == ASC_STL_256COLOR)
+    make_pal256(&c_palette_256, c_palette_ansi_vga);
+  
   state->out_file = stdout;
   if (strcmp(args.output_filename, "-"))
     state->out_file = fopen(args.output_filename, "wb");

src/colors.c

@@ -11,6 +11,10 @@ palette_t c_palette_bw = {
   }
 };
 
+palette_t c_palette_256 = {
+  .n_colors = 0
+};
+
 palette_t c_palette_ansi_discord = {
   .n_colors = 8,
   .palette = {
@@ -89,30 +93,11 @@ int closest_color(palette_t pal, rgba8 color)
   return nearest;
 }
 
-int closest_256(palette_t pal, rgba8 color)
-{
-  (void)pal;
-  if (color.r == color.g && color.g == color.b)
-  {
-    if (color.r < 8) return 16;
-    if (color.r > 248) return 231;
-    return 232 + (int)ceil((color.r - 8.0) / 247.0 * 24.0);
-  }
-  int oc = 16;
-  oc += 36 * (int)ceil(color.r / 255.0 * 5.0);
-  oc += 6  * (int)ceil(color.g / 255.0 * 5.0);
-  oc +=      (int)ceil(color.b / 255.0 * 5.0);
-  return oc;
-}
-
 rgba8 pal256_to_rgb(palette_t pal, int ndx)
 {
+  (void)pal;
   rgba8 out = { 0, 0, 0, 255 };
-  if (ndx < 16)
+  if (ndx >= 232)
-  {
-    return pal.palette[ndx];
-  }
-  else if (ndx >= 232)
   {
     int l = (ndx - 232) * 255 / 24;
     out.r = out.g = out.b = l;
@@ -129,6 +114,17 @@ rgba8 pal256_to_rgb(palette_t pal, int ndx)
   return out;      
 }
 
+void make_pal256(palette_t *dst, palette_t ansi)
+{
+  if (dst->n_colors == 256) return;
+  dst->n_colors = 256;
+  for (int i = 0; i < 256; i++)
+  {
+    rgba8 res = pal256_to_rgb(ansi, i);
+    memcpy(&dst->palette[i], &res, sizeof(rgba8));
+  }
+}
+
 float calc_brightness(rgba8 c)
 {
   return 0.2126 * c.r + 0.7152 * c.g + 0.0722 * c.b;

src/colors.h

@@ -14,13 +14,14 @@ typedef struct {
 } palette_t;
 
 extern palette_t c_palette_bw;
+extern palette_t c_palette_256;
 extern palette_t c_palette_ansi_discord;
 extern palette_t c_palette_ansi_vga;
 extern palette_t c_palette_ansi_xterm;
 
 int closest_color(palette_t pal, rgba8 color);
-int closest_256(palette_t pal, rgba8 color);
 rgba8 pal256_to_rgb(palette_t pal, int ndx);
+void make_pal256(palette_t *dst, palette_t ansi);
 bool load_palette_gpl(palette_t *pal, FILE *fp);
 bool load_palette_raw(palette_t *pal, FILE *fp);
 bool load_palette(palette_t *pal, FILE *fp);

src/commons.c

@@ -0,0 +1,39 @@
+#include "colors.h"
+#include "commons.h"
+
+void m_prepare_dither(asc_state_t *state)
+{
+  if (state->args.dither)
+  {
+    image_t *res = NULL;
+    switch (state->args.out_style)
+    {
+      case ASC_STL_BLACKWHITE:
+        res = image_dither(state->image, c_palette_bw);
+        break;
+      case ASC_STL_ANSI_VGA:
+        res = image_dither(state->image, c_palette_ansi_vga);
+        break;
+      case ASC_STL_ANSI_XTERM:
+        res = image_dither(state->image, c_palette_ansi_xterm);
+        break;
+      case ASC_STL_ANSI_DISCORD:
+        res = image_dither(state->image, c_palette_ansi_discord);
+        break;
+      case ASC_STL_256COLOR:
+        res = image_dither(state->image, c_palette_256); 
+        break;
+      case ASC_STL_PALETTE:
+        res = image_dither(state->image, *state->palette);
+        break;
+      case ASC_STL_TRUECOLOR:
+      case ASC_STL_ENDL:
+        break;
+    }
+    if (res != NULL)
+    {
+      image_unload(state->image);
+      state->image = res;
+    }
+  }
+}

src/commons.h

@@ -0,0 +1,8 @@
+#ifndef _COMMONS_H_
+#define _COMMONS_H_
+
+#include "args.h"
+
+void m_prepare_dither(asc_state_t *state);
+
+#endif

src/image.h

@@ -12,7 +12,6 @@ typedef struct {
 
 typedef rgba8 (*dither_quantizer_t)(rgba8 clr, void *param);
 
-
 image_t *image_load(FILE *file);
 image_t *image_resize(image_t *img, int width, int height);
 image_t *image_dither(image_t *img, palette_t palette);

src/mod_blocks.c

@@ -2,18 +2,12 @@
 #include "mod_blocks.h"
 #include "image.h"
 #include "colors.h"
+#include "commons.h"
 
 const char *BLOCKS[4] = { " ", "\xe2\x96\x80", "\xe2\x96\x84", "\xe2\x96\x88" };
 const char *BLOCKS_ESC[4] = { " ", "\\u2580", "\\u2584", "\\u2588" };
 
 
-rgba8 __to_256(rgba8 c, void *p)
-{
-  (void)p;
-  return pal256_to_rgb(c_palette_ansi_vga, closest_256(c_palette_ansi_vga, c));
-}
-
-
 void mod_blocks_prepare(asc_state_t *state)
 {
   int w, h;
@@ -21,49 +15,8 @@ void mod_blocks_prepare(asc_state_t *state)
       state->source_image->width, state->source_image->height,
       state->args.width, state->args.height * 2, &w, &h);
   h = (h / 2) * 2;
-  if (state->args.verbose)
-  {
-    fprintf(stderr, "src: %dx%d\n",
-        state->source_image->width,
-        state->source_image->height);
-    fprintf(stderr, "tgt: %dx%d\n", state->args.width, state->args.height * 2);
-    fprintf(stderr, "dst: %dx%d\n", w, h);
-  }
   state->image = image_resize(state->source_image, w, h);
-  // TODO: dither
+  m_prepare_dither(state);
-  if (state->args.dither)
-  {
-    image_t *res = NULL;
-    switch (state->args.out_style)
-    {
-      case ASC_STL_BLACKWHITE:
-        res = image_dither(state->image, c_palette_bw);
-        break;
-      case ASC_STL_ANSI_VGA:
-        res = image_dither(state->image, c_palette_ansi_vga);
-        break;
-      case ASC_STL_ANSI_XTERM:
-        res = image_dither(state->image, c_palette_ansi_xterm);
-        break;
-      case ASC_STL_ANSI_DISCORD:
-        res = image_dither(state->image, c_palette_ansi_discord);
-        break;
-      case ASC_STL_256COLOR:
-        res = image_dither_fn(state->image, __to_256, NULL);
-        break;
-      case ASC_STL_PALETTE:
-        res = image_dither(state->image, *state->palette);
-        break;
-      case ASC_STL_TRUECOLOR:
-      case ASC_STL_ENDL:
-        break;
-    }
-    if (res != NULL)
-    {
-      image_unload(state->image);
-      state->image = res;
-    }
-  }
 }
 
 void __start_output(asc_state_t state)
@@ -254,8 +207,8 @@ void __put_pixel(asc_state_t state, rgba8 top, rgba8 bot, bool final)
       break;
     case ASC_STL_256COLOR:
       {
-        int index_top = closest_256(c_palette_ansi_vga, top),
+        int index_top = closest_color(c_palette_256, top),
-            index_bot = closest_256(c_palette_ansi_vga, bot);
+            index_bot = closest_color(c_palette_256, bot);
         __putc_256(fp, fmt, final, index_top, index_bot, c_palette_ansi_vga);
       }
       break;