Merge pull request #423 from ffawkes/png-output

Support PNG output on older libvips versions

vips.h

@@ -336,7 +336,7 @@ vips_jpegsave_bridge(VipsImage *in, void **buf, size_t *len, int strip, int qual
 
 int
 vips_pngsave_bridge(VipsImage *in, void **buf, size_t *len, int strip, int compression, int quality, int interlace, int palette, int speed) {
-#if (VIPS_MAJOR_VERSION >= 8 && VIPS_MINOR_VERSION >= 7)
+#if (VIPS_MAJOR_VERSION >= 8 && VIPS_MINOR_VERSION >= 12)
 	int effort = 10 - speed;
 	return vips_pngsave_buffer(in, buf, len,
 		"strip", INT_TO_GBOOLEAN(strip),
@@ -348,6 +348,15 @@ vips_pngsave_bridge(VipsImage *in, void **buf, size_t *len, int strip, int compr
 		"effort", effort,
 		NULL
 	);
+#elif (VIPS_MAJOR_VERSION >= 8 && VIPS_MINOR_VERSION >= 7)
+	return vips_pngsave_buffer(in, buf, len,
+		"strip", INT_TO_GBOOLEAN(strip),
+		"compression", compression,
+		"interlace", INT_TO_GBOOLEAN(interlace),
+		"filter", VIPS_FOREIGN_PNG_FILTER_ALL,
+		"palette", INT_TO_GBOOLEAN(palette),
+		NULL
+	);
 #else
 	return vips_pngsave_buffer(in, buf, len,
 		"strip", INT_TO_GBOOLEAN(strip),