Make img2twit message length configurable at runtime, improve the initial

guess by smoothing hard colour gradients, and fixed the bitstack copy
constructor to avoid corruption on exit.

git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@3523 92316355-f0b4-4df1-b90c-862c8a59935f

examples/img2twit.cpp

@@ -1,3 +1,15 @@
+/*
+ *  img2twit      Image to short text message encoder/decoder
+ *  Copyright (c) 2009 Sam Hocevar <sam@hocevar.net>
+ *                All Rights Reserved
+ *
+ *  This program is free software. It comes without any warranty, to
+ *  the extent permitted by applicable law. You can redistribute it
+ *  and/or modify it under the terms of the Do What The Fuck You Want
+ *  To Public License, Version 2, as published by Sam Hocevar. See
+ *  http://sam.zoy.org/wtfpl/COPYING for more details.
+ */
+
 #include "config.h"
 
 #include <stdio.h>
@@ -56,6 +68,19 @@ static const uint32_t unichars[] =
 /* How does the algorithm work: one point per cell, or two */
 #define POINTS_PER_CELL 2
 
+/*
+ * These values can be overwritten at runtime
+ */
+
+/* Debug mode */
+static bool DEBUG_MODE = false;
+
+/* The maximum message length */
+static int MAX_MSG_LEN = 140;
+
+/* Iterations per point -- larger means slower but nicer */
+static int ITERATIONS_PER_POINT = 50;
+
 /* The range value for point parameters: X Y, red/green/blue, "strength"
  * Tested values (on Mona Lisa) are:
  *  16 16 5 5 5 2 -> 0.06511725914
@@ -70,17 +95,6 @@ static unsigned int RANGE_G = 6;
 static unsigned int RANGE_B = 6;
 static unsigned int RANGE_S = 1;
 
-/*
- * These values can be overwritten at runtime
- */
-
-static bool DEBUG = false;
-
-/* The maximum message length */
-static int MAX_MSG_LEN = 1140;
-
-static int ITERATIONS_PER_POINT = 50;
-
 /*
  * These values are computed at runtime
  */
@@ -273,6 +287,13 @@ public:
 private:
     bitstack(uint32_t i) { alloc(); init(i); }
 
+    bitstack(bitstack &b)
+    {
+        alloc();
+        msb = b.msb;
+        memcpy(digits, b.digits, (MAX_MSG_LEN + 1) * sizeof(uint32_t));
+    }
+
     bitstack(bitstack const &b)
     {
         alloc();
@@ -686,7 +707,7 @@ static void analyse(pipi_image_t *src)
     for(unsigned int dy = 0; dy < dh; dy++)
         for(unsigned int dx = 0; dx < dw; dx++)
         {
-            float min = 1.1f, max = -0.1f;
+            float min = 1.1f, max = -0.1f, mr = 0.0f, mg = 0.0f, mb = 0.0f;
             float total = 0.0;
             int xmin = 0, xmax = 0, ymin = 0, ymax = 0;
             int npixels = 0;
@@ -699,6 +720,11 @@ static void analyse(pipi_image_t *src)
                     lum += data[4 * (ix + iy * p->w) + 0];
                     lum += data[4 * (ix + iy * p->w) + 1];
                     lum += data[4 * (ix + iy * p->w) + 2];
+                    lum /= 3;
+
+                    mr += data[4 * (ix + iy * p->w) + 0];
+                    mg += data[4 * (ix + iy * p->w) + 1];
+                    mb += data[4 * (ix + iy * p->w) + 2];
 
                     if(lum < min)
                     {
@@ -719,6 +745,9 @@ static void analyse(pipi_image_t *src)
                 }
 
             total /= npixels;
+            mr /= npixels;
+            mg /= npixels;
+            mb /= npixels;
 
             float wmin, wmax;
 
@@ -730,17 +759,19 @@ static void analyse(pipi_image_t *src)
                 wmin = 0.0, wmax = 1.0;
 
 #if 0
-add_random_point();
-add_random_point();
+            add_random_point();
+            add_random_point();
 #else
+            /* 0.80 and 0.20 were chosen empirically, it gives a 10% better
+             * initial distance. Definitely worth it. */
 #if POINTS_PER_CELL == 1
             if(total < min + (max - min) / 2)
             {
 #endif
             add_point(xmin, ymin,
-                      data[4 * (xmin + ymin * p->w) + 0],
-                      data[4 * (xmin + ymin * p->w) + 1],
-                      data[4 * (xmin + ymin * p->w) + 2],
+                      data[4 * (xmin + ymin * p->w) + 0] * 0.80 + mr * 0.20,
+                      data[4 * (xmin + ymin * p->w) + 1] * 0.80 + mg * 0.20,
+                      data[4 * (xmin + ymin * p->w) + 2] * 0.80 + mb * 0.20,
                       wmin);
 #if POINTS_PER_CELL == 1
             }
@@ -748,9 +779,9 @@ add_random_point();
             {
 #endif
             add_point(xmax, ymax,
-                      data[4 * (xmax + ymax * p->w) + 0],
-                      data[4 * (xmax + ymax * p->w) + 1],
-                      data[4 * (xmax + ymax * p->w) + 2],
+                      data[4 * (xmax + ymax * p->w) + 0] * 0.80 + mr * 0.20,
+                      data[4 * (xmax + ymax * p->w) + 1] * 0.80 + mg * 0.20,
+                      data[4 * (xmax + ymax * p->w) + 2] * 0.80 + mb * 0.20,
                       wmax);
 #if POINTS_PER_CELL == 1
             }
@@ -764,7 +795,6 @@ add_random_point();
 int main(int argc, char *argv[])
 {
     int opstats[2 * NB_OPS];
-    bitstack b;
     char const *srcname = NULL, *dstname = NULL;
     pipi_image_t *src, *tmp, *dst;
     double error = 1.0;
@@ -777,12 +807,13 @@ int main(int argc, char *argv[])
         static struct myoption long_options[] =
         {
             { "output",      1, NULL, 'o' },
+            { "length",      1, NULL, 'l' },
             { "quality",     1, NULL, 'q' },
             { "debug",       0, NULL, 'd' },
             { "help",        0, NULL, 'h' },
             { NULL,          0, NULL, 0   },
         };
-        int c = mygetopt(argc, argv, "o:q:dh", long_options, &option_index);
+        int c = mygetopt(argc, argv, "o:l:q:dh", long_options, &option_index);
 
         if(c == -1)
             break;
@@ -792,15 +823,23 @@ int main(int argc, char *argv[])
         case 'o':
             dstname = myoptarg;
             break;
+        case 'l':
+            MAX_MSG_LEN = atoi(myoptarg);
+            if(MAX_MSG_LEN < 16)
+            {
+                fprintf(stderr, "Warning: rounding minimum message length to 16\n");
+                MAX_MSG_LEN = 16;
+            }
+            break;
         case 'q':
             ITERATIONS_PER_POINT = 10 * atoi(myoptarg);
             if(ITERATIONS_PER_POINT < 0)
                 ITERATIONS_PER_POINT = 0;
-            else if(ITERATIONS_PER_POINT > 10)
-                ITERATIONS_PER_POINT = 10;
+            else if(ITERATIONS_PER_POINT > 100)
+                ITERATIONS_PER_POINT = 100;
             break;
         case 'd':
-            DEBUG = true;
+            DEBUG_MODE = true;
             break;
         case 'h':
             printf("Usage: img2twit [OPTIONS] SOURCE\n");
@@ -809,6 +848,7 @@ int main(int argc, char *argv[])
             printf("\n");
             printf("Mandatory arguments to long options are mandatory for short options too.\n");
             printf("  -o, --output <filename>   output resulting image to filename\n");
+            printf("  -l, --length <size>       message length in characters (default 140)\n");
             printf("  -q, --quality <rate>      set image quality (0 - 10) (default 5)\n");
             printf("  -d, --debug               print debug information\n");
             printf("  -h, --help                display this help and exit\n");
@@ -858,6 +898,9 @@ int main(int argc, char *argv[])
     TOTAL_CELLS = (int)(DATA_BITS / CELL_BITS);
     MAX_ITERATIONS = ITERATIONS_PER_POINT * POINTS_PER_CELL * TOTAL_CELLS;
 
+    bitstack b; /* We cannot declare this before, because MAX_MSG_LEN
+                 * wouldn't be defined. */
+
     if(dstname)
     {
         /* Decoding mode: read UTF-8 text from stdin, find each
@@ -909,7 +952,7 @@ int main(int argc, char *argv[])
     while(dw * (dh + 1) <= TOTAL_CELLS) dw++;
 
     /* Print debug information */
-    if(DEBUG)
+    if(DEBUG_MODE)
     {
         fprintf(stderr, "Maximum message size: %i\n", MAX_MSG_LEN);
         fprintf(stderr, "Available characters: %i\n", NUM_CHARACTERS);
@@ -935,7 +978,6 @@ int main(int argc, char *argv[])
         pipi_free(src);
         src = pipi_median_ext(tmp, 1, 1);
         pipi_free(tmp);
-pipi_save(src, "lol.bmp");
 
         /* Analyse image */
         analyse(src);
@@ -943,10 +985,9 @@ pipi_save(src, "lol.bmp");
         /* Render what we just computed */
         tmp = pipi_new(dw * RANGE_X, dh * RANGE_Y);
         render(tmp, 0, 0, dw * RANGE_X, dh * RANGE_Y);
-pipi_save(tmp, "lol2.bmp");
         error = pipi_measure_rmsd(src, tmp);
 
-        if(DEBUG)
+        if(DEBUG_MODE)
             fprintf(stderr, "Initial distance: %2.10g\n", error);
 
         memset(opstats, 0, sizeof(opstats));
@@ -960,7 +1001,7 @@ pipi_save(tmp, "lol2.bmp");
                 failures = 0;
             }
 
-            if(!DEBUG && !(iter % 16))
+            if(!DEBUG_MODE && !(iter % 16))
                 fprintf(stderr, "\rEncoding... %i%%",
                         iter * 100 / MAX_ITERATIONS);
 
@@ -1026,7 +1067,7 @@ pipi_save(tmp, "lol2.bmp");
                 pipi_free(tmp);
                 tmp = scrap;
 
-                if(DEBUG)
+                if(DEBUG_MODE)
                     fprintf(stderr, "%08i -.%08i %2.010g after op%i(%i)\n",
                             iter, (int)((error - besterr) * 100000000), error,
                             op1, pt);
@@ -1051,7 +1092,7 @@ pipi_save(tmp, "lol2.bmp");
             }
         }
 
-        if(DEBUG)
+        if(DEBUG_MODE)
         {
             for(int j = 0; j < 2; j++)
             {