[devel] Revised pngvalid.c 16-to-8-big conversion tests

contrib/pngminim/decoder/pngusr.dfa

@@ -7,6 +7,7 @@
 # and license in png.h
 
 # First all the build options off:
+
 everything = off
 
 # All that is required is some read code. This example switches
@@ -31,7 +32,8 @@ option FLOATING_ARITHMETIC off
 # program here, pngm2pnm, requires the following.  Take a look
 # at pnglibconf.h to find out the full set of what has to be
 # enabled to make the following work.
+
 option SETJMP on
 option STDIO on
 option READ_EXPAND on
-option READ_16BIT on
+option READ_16_TO_8 on

contrib/pngminim/encoder/pngusr.dfa

@@ -7,26 +7,29 @@
 # and license in png.h
 
 # First all the build options off:
+
 everything = off
 
-option NO_16BIT on
-
 # Switch on the write code - this makes a minimalist encoder
+
 option WRITE on
 
 # You must choose fixed or floating point arithmetic:
 # option FLOATING_POINT on
+
 option FIXED_POINT on
 
 # You must chose the internal fixed point implementation or to
 # use the system floating point.  The latter is considerably
 # smaller (by about 1kbyte on an x86 system):
 # option FLOATING_ARITHMETIC on
+
 option FLOATING_ARITHMETIC off
 
 # Your program will probably need other options.  The example
 # program here, pnm2pngm, requires the following.  Take a look
 # at pnglibconf.h to find out the full set of what has to be
 # enabled to make the following work.
+
 option SETJMP on
 option STDIO on

contrib/pngminim/preader/pngusr.dfa

@@ -7,18 +7,22 @@
 # and license in png.h
 
 # First all the build options off:
+
 everything = off
 
 # Just switch on the progressive read code
+
 option PROGRESSIVE_READ on
 
 # You may choose fixed or floating point APIs:
 # option FLOATING_POINT on
+
 option FIXED_POINT on
 
 # You must chose the internal fixed point implementation or to
 # use the system floating point.  The latter is considerably
 # smaller (by about 1kbyte on an x86 system):
+
 option FLOATING_ARITHMETIC on
 # option FLOATING_ARITHMETIC off
 
@@ -26,6 +30,7 @@ option FLOATING_ARITHMETIC on
 # program here, rpng2-x, requires the following.  Take a look
 # at pnglibconf.h to find out the full set of what has to be
 # enabled to make the following work.
+
 option SETJMP on
 option STDIO on
 option READ_bKGD on

pngvalid.c

@@ -1,7 +1,7 @@
 
 /* pngvalid.c - validate libpng by constructing then reading png files.
  *
- * Last changed in libpng 1.5.0 [August 26, 2010]
+ * Last changed in libpng 1.5.0 [August 27, 2010]
  * Copyright (c) 2010 Glenn Randers-Pehrson
  * Written by John C. Bowler
  *
@@ -2776,7 +2776,11 @@ gamma_info_imp(gamma_display *dp, png_structp pp, png_infop pi)
     * PNG_MAX_GAMMA_8 when doing the following.
     */
    if (dp->strip16)
-      png_set_strip_16(pp);
+#     ifdef PNG_READ_16_TO_8
+         png_set_strip_16(pp);
+#     else
+         png_error(pp, "strip16 (16 to 8 bit conversion) not supported");
+#     endif
 
    png_read_update_info(pp, pi);
 
@@ -3355,7 +3359,7 @@ static void perform_gamma_sbit_tests(png_modifier *pm, int speed)
 /* Note that this requires a 16 bit source image but produces 8 bit output, so
  * we only need the 16bit write support.
  */
-#ifdef PNG_WRITE_16BIT_SUPPORTED
+#ifdef PNG_16_TO_8_SUPPORTED
 static void perform_gamma_strip16_tests(png_modifier *pm, int speed)
 {
 #  ifndef PNG_MAX_GAMMA_8
@@ -3408,7 +3412,7 @@ static void perform_gamma_strip16_tests(png_modifier *pm, int speed)
       }
    }
 }
-#endif
+#endif /* 16 to 8 bit conversion */
 
 static void
 perform_gamma_test(png_modifier *pm, int speed, int summary)
@@ -3461,7 +3465,7 @@ perform_gamma_test(png_modifier *pm, int speed, int summary)
 #endif
    }
 
-#ifdef PNG_WRITE_16BIT_SUPPORTED
+#ifdef PNG_16_TO_8_SUPPORTED
    /* The 16 to 8 bit strip operations: */
    pm->error_gray_2 = pm->error_gray_4 = pm->error_gray_8 = pm->error_gray_16 =
    pm->error_color_8 = pm->error_color_16 = 0;

scripts/pnglibconf.dfa

@@ -291,6 +291,10 @@ setting USER_CHUNK_MALLOC_MAX default 0
 
 option READ enables READ_INTERLACING
 
+# Disabling READ_16BIT does not disable reading 16-bit PNG files, but it
+# forces them to be chopped down to 8-bit, and disables any 16-bit
+# processing after that has happened.
+
 option READ_16BIT requires READ enables 16BIT
 
 option READ_QUANTIZE requires READ
@@ -345,6 +349,8 @@ option READ_16_TO_8_ACCURATE_SCALE requires READ disabled
 
 option WRITE
 
+# Disabling WRITE_16BIT prevents 16-bit PNG files from being
+# generated.
 option WRITE_16BIT requires WRITE enables 16BIT
 
 option WRITE_TRANSFORMS requires WRITE