[devel] Fix more inconsistencies from the swap of 16_TO_8 APIs.

pngvalid still fails.

png.h

@@ -1426,12 +1426,12 @@ PNG_FIXED_EXPORT(215, void, png_set_background_fixed, (png_structp png_ptr,
 #ifdef PNG_READ_16_TO_8_SUPPORTED
 #  ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
 /* Scale a 16-bit depth file down to 8-bit, accurately. */
-PNG_EXPORT(48, void, png_set_scale_16, (png_structp png_ptr));
+PNG_EXPORT(229, void, png_set_scale_16, (png_structp png_ptr));
 #  endif
 
 #  ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
 /* Strip the second byte of information from a 16-bit depth file. */
-PNG_EXPORT(229, void, png_set_strip_16, (png_structp png_ptr));
+PNG_EXPORT(48, void, png_set_strip_16, (png_structp png_ptr));
 #  endif
 #endif
 

pngread.c

@@ -1289,18 +1289,21 @@ png_read_png(png_structp png_ptr, png_infop info_ptr,
 #ifdef PNG_READ_16_TO_8_SUPPORTED
    /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
     */
-#  ifdef PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
+#  ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
    if (transforms & PNG_TRANSFORM_SCALE_16)
       png_set_scale_16(png_ptr);
+#    ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+   else
+
+#    endif
 #  endif
 #  ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
-  /* Added at libpng-1.5.4. "strip_16" produces the same result that it
-   * did in earlier versions, while "scale_16" is now more accurate.
-   */
-   else
+     /* Added at libpng-1.5.4. "strip_16" produces the same result that it
+      * did in earlier versions, while "scale_16" is now more accurate.
+      */
      if (transforms & PNG_TRANSFORM_STRIP_16)
         png_set_strip_16(png_ptr);
-#endif
+#  endif
 #endif
 
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED

scripts/symbols.def

@@ -234,4 +234,4 @@ EXPORTS
  png_set_text_compression_method @226
  png_set_alpha_mode @227
  png_set_alpha_mode_fixed @228
- png_set_chop_16 @229
+ png_set_scale_16 @229