Test changes

Most of these are back-portable to earlier versions (contrib/libtests
should just work with earlier versions), however the 1.7 specific
changes in pngvalid mean that it probably won't work against 1.7 without
the commits following this one.

Signed-off-by: John Bowler <jbowler@acm.org>

contrib/tools/dynamic-range.c

@@ -0,0 +1,208 @@
+/* dynamic-range.c
+ *
+ * Last changed in libpng 1.7.0
+ *
+ * COPYRIGHT: Written by John Cunningham Bowler, 2015
+ * To the extent possible under law, the author has waived all copyright and
+ * related or neighboring rights to this work.  This work is published from:
+ * United States.
+ *
+ * Find the dynamic range of a given gamma encoding given a (linear) precision
+ * and a maximum number of encoded values.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <float.h>
+#include <math.h>
+#include <assert.h>
+
+double range(unsigned int steps, double factor, double gamma)
+{
+   return pow((steps * (pow(factor, 1/gamma) - 1)), gamma);
+}
+
+double max_range_gamma(unsigned int steps, double factor, double *max_range,
+      double glo, double rlo, double gmid, double rmid, double ghi, double rhi)
+{
+   /* Given three values which contain a peak value (so rmid > rlo and rmid >
+    * rhi) find the peak by repeated division of the range.  The algorithm is to
+    * find the range for two gamma values mid-way between the two pairs
+    * (glo,gmid), (ghi,gmid) then find the max; this gives us a new glo/ghi
+    * which must be half the distance apart of the previous pair.
+    */
+   double gammas[5];
+   double ranges[5];
+
+   gammas[0] = glo;  ranges[0] = rlo;
+   gammas[2] = gmid; ranges[2] = rmid;
+   gammas[4] = ghi;  ranges[4] = rhi;
+
+   for (;;)
+   {
+      int i, m;
+
+      ranges[1] = range(steps, factor, gammas[1] = (gammas[0]+gammas[2])/2);
+      ranges[3] = range(steps, factor, gammas[3] = (gammas[2]+gammas[4])/2);
+
+      for (m=1, i=2; i<4; ++i)
+         if (ranges[i] >= ranges[m])
+            m = i;
+
+      assert(gammas[0] < gammas[m] && gammas[m] < gammas[4]);
+      assert(ranges[0] < ranges[m] && ranges[m] > ranges[4]);
+
+      gammas[0] = gammas[m-1]; ranges[0] = ranges[m-1];
+      gammas[4] = gammas[m+1]; ranges[4] = ranges[m+1];
+      gammas[2] = gammas[m];   ranges[2] = ranges[m];
+
+      if (((gammas[4] - gammas[0])/gammas[2]-1) < 3*DBL_EPSILON ||
+          ((ranges[2] - ranges[0])/ranges[2]-1) < 6*DBL_EPSILON)
+      {
+         *max_range = ranges[2];
+         return gammas[2];
+      }
+   }
+}
+
+double best_gamma(unsigned int values, double precision, double *best_range)
+{
+   /* The 'guess' gamma value is determined by the following formula, which is
+    * itself derived from linear regression using values returned by this
+    * program:
+    */
+   double gtry = values * precision / 2.736;
+   double rtry;
+
+   /* 'values' needs to be the number of steps after the first, we have to
+    * reserve the first value, 0, for 0, so subtract 2 from values.  precision
+    * must be adjusted to the step factor.
+    */
+   values -= 2U;
+   precision += 1;
+   rtry = range(values, precision, gtry);
+
+   /* Now find two values either side of gtry with a lower range. */
+   {
+      double glo, ghi, rlo, rhi, gbest, rbest;
+
+      glo = gtry;
+      do
+      {
+         glo *= 0.9;
+         rlo = range(values, precision, glo);
+      }
+      while (rlo >= rtry);
+
+      ghi = gtry;
+      do
+      {
+         ghi *= 1.1;
+         rhi = range(values, precision, ghi);
+      }
+      while (rhi >= rtry);
+
+      gbest = max_range_gamma(values, precision, &rbest,
+            glo, rlo, gtry, rtry, ghi, rhi);
+
+      *best_range = rbest / precision;
+      return gbest;
+   }
+}
+
+double linear_regression(double precision, double *bp)
+{
+   unsigned int values, count = 0;
+   double g_sum = 0, g2_sum = 0, v_sum = 0, v2_sum = 0, gv_sum = 0;
+
+   /* Perform simple linear regression to get:
+    *
+    *    gamma = a + b.values
+    */
+   for (values = 128; values < 65536; ++values, ++count)
+   {
+      double range;
+      double gamma = best_gamma(values, precision, &range);
+
+      g_sum += gamma;
+      g2_sum += gamma * gamma;
+      v_sum += values;
+      v2_sum += values * (double)values;
+      gv_sum += gamma * values;
+      /* printf("%u %g %g\n", values, gamma, range); */
+   }
+
+   g_sum /= count;
+   g2_sum /= count;
+   v_sum /= count;
+   v2_sum /= count;
+   gv_sum /= count;
+
+   {
+      double b = (gv_sum - g_sum * v_sum) / (v2_sum - v_sum * v_sum);
+      *bp = b;
+      return g_sum - b * v_sum;
+   }
+}
+
+int
+main(int argc, const char **argv)
+{
+   double precision = argc == 2 ? atof(argv[1]) : 0;
+
+   /* Perform a second linear regression here on b:
+    *
+    *    b = bA + bB * precision
+    */
+   if (precision == 0)
+   {
+      double b_sum = 0, b2_sum = 0, p_sum = 0, p2_sum = 0, bp_sum = 0,
+             a_sum = 0, count = 0;
+
+      for (precision = .001; precision <= 0.01; precision += .001, count += 1)
+      {
+         double b;
+         double a = linear_regression(precision, &b);
+
+         b_sum += b;
+         b2_sum += b * b;
+         p_sum += precision;
+         p2_sum += precision * precision;
+         bp_sum += b * precision;
+         a_sum += a;
+      }
+
+      b_sum /= count;
+      b2_sum /= count;
+      p_sum /= count;
+      p2_sum /= count;
+      bp_sum /= count;
+      a_sum /= count;
+
+      {
+         double bB = (bp_sum - b_sum * p_sum) / (p2_sum - p_sum * p_sum);
+         double bA = b_sum - bB * p_sum;
+
+         printf("a = %g, b = %g + precision/%g\n", a_sum, bA, 1/bB);
+      }
+   }
+
+   else
+   {
+      unsigned int bits;
+      double b;
+      double a = linear_regression(precision, &b);
+      printf("precision %g: gamma = %g + values*%g\n", precision, a, b);
+
+      /* For information, given a precision: */
+      for (bits=7U; bits <= 16U; ++bits)
+      {
+         unsigned int values = 1U<<bits;
+         double gamma = values*precision/2.736;
+         double r = range(values-2U, 1+precision, gamma);
+
+         printf("bits: %u, gamma: %g, range: 1:%g\n", bits, gamma, r);
+      }
+   }
+
+   return 0;
+}

contrib/tools/pngfix.c

@@ -52,7 +52,8 @@
 #ifdef PNG_SETJMP_SUPPORTED
 #include <setjmp.h>
 
-#if defined(PNG_READ_SUPPORTED) && defined(PNG_EASY_ACCESS_SUPPORTED)
+#if defined(PNG_READ_SUPPORTED) && defined(PNG_EASY_ACCESS_SUPPORTED) &&\
+   defined(PNG_READ_DEINTERLACE_SUPPORTED)
 /* zlib.h defines the structure z_stream, an instance of which is included
  * in this structure and is required for decompressing the LZ compressed
  * data in PNG files.
@@ -4030,7 +4031,7 @@ main(void)
 int
 main(void)
 {
-   fprintf(stderr, "pngfix does not work without read support\n");
+   fprintf(stderr, "pngfix does not work without read deinterlace support\n");
    return 77;
 }
 #endif /* PNG_READ_SUPPORTED && PNG_EASY_ACCESS_SUPPORTED */
@@ -4042,4 +4043,3 @@ main(void)
    return 77;
 }
 #endif /* PNG_SETJMP_SUPPORTED */
-