$ diff -ur gnuplot-5.0.4{.old,}
diff -ur gnuplot-5.0.4.old/ChangeLog gnuplot-5.0.4/ChangeLog
--- gnuplot-5.0.4.old/ChangeLog	2016-07-20 05:22:29.000000000 +0200
+++ gnuplot-5.0.4/ChangeLog	2016-07-21 17:45:11.000000000 +0200
@@ -1,3 +1,10 @@
+2016-07-21  Ethan A Merritt  <merritt@u.washington.edu>
+
+	* src/term_api.h:  Define TERM_POLYGON_PIXELS.
+	* src/graphics.c (plot_image_or_update_axes):  If this flag is set,
+	implement "plot ... with image pixels" using term->filled_polygon()
+	rather than term->fillbox().
+
 2016-07-19  Jun Takimoto <takimoto-j@kba.biglobe.ne.jp>
 
 	* term/aquaterm.trm:  The AQUA_boxfill() routine scales very badly 
Binary files gnuplot-5.0.4.old/docs/gnuplot.pdf and gnuplot-5.0.4/docs/gnuplot.pdf differ
diff -ur gnuplot-5.0.4.old/src/graphics.c gnuplot-5.0.4/src/graphics.c
--- gnuplot-5.0.4.old/src/graphics.c	2016-07-06 06:43:36.000000000 +0200
+++ gnuplot-5.0.4/src/graphics.c	2016-07-21 17:43:44.000000000 +0200
@@ -4835,7 +4835,8 @@
 				corners[0].style = FS_TRANSPARENT_SOLID + (alpha<<4);
 			}
 
-			if (rectangular_image && term->fillbox) {
+			if (rectangular_image && term->fillbox
+			&&  !(term->flags & TERM_POLYGON_PIXELS)) {
 			    /* Some terminals (canvas) can do filled rectangles */
 			    /* more efficiently than filled polygons. */
 			    (*term->fillbox)( corners[0].style,
diff -ur gnuplot-5.0.4.old/src/term_api.h gnuplot-5.0.4/src/term_api.h
--- gnuplot-5.0.4.old/src/term_api.h	2016-01-19 00:51:59.000000000 +0100
+++ gnuplot-5.0.4/src/term_api.h	2016-07-21 17:39:07.000000000 +0200
@@ -261,6 +261,7 @@
 #define TERM_IS_LATEX        (1<<13)	/* text uses TeX markup            */
 #define TERM_EXTENDED_COLOR  (1<<14)	/* uses EXTENDED_COLOR_SPECS       */
 #define TERM_NULL_SET_COLOR  (1<<15)	/* no support for RGB color        */
+#define TERM_POLYGON_PIXELS  (1<<16)	/* filledpolygon rather than fillbox */
 
 /* The terminal interface structure --- heart of the terminal layer.
  *
diff -ur gnuplot-5.0.4.old/src/version.c gnuplot-5.0.4/src/version.c
--- gnuplot-5.0.4.old/src/version.c	2016-07-20 05:23:21.000000000 +0200
+++ gnuplot-5.0.4/src/version.c	2016-07-21 17:50:12.000000000 +0200
@@ -44,7 +44,7 @@
 #ifdef DEVELOPMENT_VERSION
 #include "timestamp.h"
 #else
-const char gnuplot_date[] = "2016-07-19 ";
+const char gnuplot_date[] = "2016-07-21 ";
 #endif
 const char gnuplot_copyright[] = "Copyright (C) 1986-1993, 1998, 2004, 2007-2016";