shithub: imgtools

Download patch

ref: 417aaddf58751d731709803032ed2dd09fa68896
parent: 5383442fa1cba98ca2f8638e9f8ef556d1f439ae
author: Sigrid Solveig Haflínudóttir <ftrvxmtrx@gmail.com>
date: Fri Apr 23 06:35:36 EDT 2021 

make uint8 to float conversion faster


--- a/mkfile
+++ b/mkfile
@@ -10,3 +10,4 @@
 default:V: all
 
 </sys/src/cmd/mkmany
+#LDFLAGS=-p
--- a/stb_image_resize.h
+++ b/stb_image_resize.h
@@ -547,6 +547,42 @@
 static const float stbir__max_uint16_as_float = 65535.0f;
 static const double stbir__max_uint32_as_float = 4294967295.0;
 
+static const float stbir__uint8_to_float[] = {
+#define D(x) (x/255.0f)
+      D(0.0f),   D(1.0f),   D(2.0f),   D(3.0f),   D(4.0f),   D(5.0f),   D(6.0f),   D(7.0f),
+      D(8.0f),   D(9.0f),  D(10.0f),  D(11.0f),  D(12.0f),  D(13.0f),  D(14.0f),  D(15.0f),
+     D(16.0f),  D(17.0f),  D(18.0f),  D(19.0f),  D(20.0f),  D(21.0f),  D(22.0f),  D(23.0f),
+     D(24.0f),  D(25.0f),  D(26.0f),  D(27.0f),  D(28.0f),  D(29.0f),  D(30.0f),  D(31.0f),
+     D(32.0f),  D(33.0f),  D(34.0f),  D(35.0f),  D(36.0f),  D(37.0f),  D(38.0f),  D(39.0f),
+     D(40.0f),  D(41.0f),  D(42.0f),  D(43.0f),  D(44.0f),  D(45.0f),  D(46.0f),  D(47.0f),
+     D(48.0f),  D(49.0f),  D(50.0f),  D(51.0f),  D(52.0f),  D(53.0f),  D(54.0f),  D(55.0f),
+     D(56.0f),  D(57.0f),  D(58.0f),  D(59.0f),  D(60.0f),  D(61.0f),  D(62.0f),  D(63.0f),
+     D(64.0f),  D(65.0f),  D(66.0f),  D(67.0f),  D(68.0f),  D(69.0f),  D(70.0f),  D(71.0f),
+     D(72.0f),  D(73.0f),  D(74.0f),  D(75.0f),  D(76.0f),  D(77.0f),  D(78.0f),  D(79.0f),
+     D(80.0f),  D(81.0f),  D(82.0f),  D(83.0f),  D(84.0f),  D(85.0f),  D(86.0f),  D(87.0f),
+     D(88.0f),  D(89.0f),  D(90.0f),  D(91.0f),  D(92.0f),  D(93.0f),  D(94.0f),  D(95.0f),
+     D(96.0f),  D(97.0f),  D(98.0f),  D(99.0f),  D(100.0f), D(101.0f), D(102.0f), D(103.0f),
+     D(104.0f), D(105.0f), D(106.0f), D(107.0f), D(108.0f), D(109.0f), D(110.0f), D(111.0f),
+     D(112.0f), D(113.0f), D(114.0f), D(115.0f), D(116.0f), D(117.0f), D(118.0f), D(119.0f),
+     D(120.0f), D(121.0f), D(122.0f), D(123.0f), D(124.0f), D(125.0f), D(126.0f), D(127.0f),
+     D(128.0f), D(129.0f), D(130.0f), D(131.0f), D(132.0f), D(133.0f), D(134.0f), D(135.0f),
+     D(136.0f), D(137.0f), D(138.0f), D(139.0f), D(140.0f), D(141.0f), D(142.0f), D(143.0f),
+     D(144.0f), D(145.0f), D(146.0f), D(147.0f), D(148.0f), D(149.0f), D(150.0f), D(151.0f),
+     D(152.0f), D(153.0f), D(154.0f), D(155.0f), D(156.0f), D(157.0f), D(158.0f), D(159.0f),
+     D(160.0f), D(161.0f), D(162.0f), D(163.0f), D(164.0f), D(165.0f), D(166.0f), D(167.0f),
+     D(168.0f), D(169.0f), D(170.0f), D(171.0f), D(172.0f), D(173.0f), D(174.0f), D(175.0f),
+     D(176.0f), D(177.0f), D(178.0f), D(179.0f), D(180.0f), D(181.0f), D(182.0f), D(183.0f),
+     D(184.0f), D(185.0f), D(186.0f), D(187.0f), D(188.0f), D(189.0f), D(190.0f), D(191.0f),
+     D(192.0f), D(193.0f), D(194.0f), D(195.0f), D(196.0f), D(197.0f), D(198.0f), D(199.0f),
+     D(200.0f), D(201.0f), D(202.0f), D(203.0f), D(204.0f), D(205.0f), D(206.0f), D(207.0f),
+     D(208.0f), D(209.0f), D(210.0f), D(211.0f), D(212.0f), D(213.0f), D(214.0f), D(215.0f),
+     D(216.0f), D(217.0f), D(218.0f), D(219.0f), D(220.0f), D(221.0f), D(222.0f), D(223.0f),
+     D(224.0f), D(225.0f), D(226.0f), D(227.0f), D(228.0f), D(229.0f), D(230.0f), D(231.0f),
+     D(232.0f), D(233.0f), D(234.0f), D(235.0f), D(236.0f), D(237.0f), D(238.0f), D(239.0f),
+     D(240.0f), D(241.0f), D(242.0f), D(243.0f), D(244.0f), D(245.0f), D(246.0f), D(247.0f),
+     D(248.0f), D(249.0f), D(250.0f), D(251.0f), D(252.0f), D(253.0f), D(254.0f), D(255.0f), 
+#undef D
+};
 
 static stbir__inline int stbir__min(int a, int b)
 {
@@ -1258,7 +1294,7 @@
             int decode_pixel_index = x * channels;
             int input_pixel_index = stbir__edge_wrap(edge_horizontal, x, input_w) * channels;
             for (c = 0; c < channels; c++)
-                decode_buffer[decode_pixel_index + c] = ((float)((const unsigned char*)input_data)[input_pixel_index + c]) / stbir__max_uint8_as_float;
+                decode_buffer[decode_pixel_index + c] = stbir__uint8_to_float[((const unsigned char*)input_data)[input_pixel_index + c]];
         }
         break;
 
@@ -1271,7 +1307,7 @@
                 decode_buffer[decode_pixel_index + c] = stbir__srgb_uchar_to_linear_float[((const unsigned char*)input_data)[input_pixel_index + c]];
 
             if (!(stbir_info->flags&STBIR_FLAG_ALPHA_USES_COLORSPACE))
-                decode_buffer[decode_pixel_index + alpha_channel] = ((float)((const unsigned char*)input_data)[input_pixel_index + alpha_channel]) / stbir__max_uint8_as_float;
+                decode_buffer[decode_pixel_index + alpha_channel] = stbir__uint8_to_float[((const unsigned char*)input_data)[input_pixel_index + alpha_channel]];
         }
         break;