Bitmap: Make the hard light lookup table constexpr

src/bitmap.cpp

@@ -18,6 +18,7 @@
 // Headers
 #define _USE_MATH_DEFINES
 #include <cmath>
+#include <array>
 #include <cstdlib>
 #include <cstring>
 #include <algorithm>
@@ -803,21 +804,28 @@ void Bitmap::ClearRect(Rect const& dst_rect) {
 }
 
 // Hard light lookup table mapping source color to destination color
-static uint8_t hard_light_lookup[256][256];
+// FIXME: Replace this with std::array<std::array<uint8_t,256>,256> when we have C++17
+struct HardLightTable {
+	uint8_t table[256][256] = {};
+};
 
-static void make_hard_light_lookup() {
+static constexpr HardLightTable make_hard_light_lookup() {
+	HardLightTable hl;
 	for (int i = 0; i < 256; ++i) {
 		for (int j = 0; j < 256; ++j) {
 			int res = 0;
 			if (i <= 128)
 				res = (2 * i * j) / 255;
 			else
 				res = 255 - 2 * (255 - i) * (255 - j) / 255;
-			hard_light_lookup[i][j] = res > 255 ? 255 : res < 0 ? 0 : res;
+			hl.table[i][j] = res > 255 ? 255 : res < 0 ? 0 : res;
 		}
 	}
+	return hl;
 }
 
+constexpr auto hard_light = make_hard_light_lookup();
+
 // Saturation Tone Inline: Changes a pixel saturation
 static inline void saturation_tone(uint32_t &src_pixel, int saturation, int rs, int gs, int bs, int as) {
 	// Algorithm from OpenPDN (MIT license)
@@ -842,10 +850,10 @@ static inline void saturation_tone(uint32_t &src_pixel, int saturation, int rs,
 }
 
 // Color Tone Inline: Changes color of a pixel by hard light table
-static inline void color_tone(uint32_t &src_pixel, Tone tone, uint8_t hard_light_lookup[256][256], int rs, int gs, int bs, int as) {
-	src_pixel = ((uint32_t)hard_light_lookup[tone.red][(src_pixel >> rs) & 0xFF] << rs)
-		| ((uint32_t)hard_light_lookup[tone.green][(src_pixel >> gs) & 0xFF] << gs)
-		| ((uint32_t)hard_light_lookup[tone.blue][(src_pixel >> bs) & 0xFF] << bs)
+static inline void color_tone(uint32_t &src_pixel, Tone tone, int rs, int gs, int bs, int as) {
+	src_pixel = ((uint32_t)hard_light.table[tone.red][(src_pixel >> rs) & 0xFF] << rs)
+		| ((uint32_t)hard_light.table[tone.green][(src_pixel >> gs) & 0xFF] << gs)
+		| ((uint32_t)hard_light.table[tone.blue][(src_pixel >> bs) & 0xFF] << bs)
 		| ((uint32_t)((src_pixel >> as) & 0xFF) << as);
 }
 
@@ -870,13 +878,6 @@ void Bitmap::ToneBlit(int x, int y, Bitmap const& src, Rect const& src_rect, con
 		x, y,
 		src_rect.width, src_rect.height);
 
-	// To implement Saturation and Color:
-	static bool index_made = false;
-	if (!index_made) {
-		make_hard_light_lookup();
-		index_made = true;
-	}
-
 	int as = pixel_format.a.shift;
 	int rs = pixel_format.r.shift;
 	int gs = pixel_format.g.shift;
@@ -900,7 +901,7 @@ void Bitmap::ToneBlit(int x, int y, Bitmap const& src, Rect const& src_rect, con
 						continue;
 
 					saturation_tone(pixels[j], sat, rs, gs, bs, as);
-					color_tone(pixels[j], tone, hard_light_lookup, rs, gs, bs, as);
+					color_tone(pixels[j], tone, rs, gs, bs, as);
 				}
 			}
 		}
@@ -909,7 +910,7 @@ void Bitmap::ToneBlit(int x, int y, Bitmap const& src, Rect const& src_rect, con
 				pixels += next_row;
 				for (uint16_t j = 0; j < limit_width; ++j) {
 					saturation_tone(pixels[j], sat, rs, gs, bs, as);
-					color_tone(pixels[j], tone, hard_light_lookup, rs, gs, bs, as);
+					color_tone(pixels[j], tone, rs, gs, bs, as);
 				}
 			}
 		}
@@ -949,15 +950,15 @@ void Bitmap::ToneBlit(int x, int y, Bitmap const& src, Rect const& src_rect, con
 					if ((uint8_t)((pixels[j] >> as) & 0xFF) == 0)
 						continue;
 
-					color_tone(pixels[j], tone, hard_light_lookup, rs, gs, bs, as);
+					color_tone(pixels[j], tone, rs, gs, bs, as);
 				}
 			}
 		}
 		else {
 			for (uint16_t i = 0; i < limit_height; ++i) {
 				pixels += next_row;
 				for (uint16_t j = 0; j < limit_width; ++j) {
-					color_tone(pixels[j], tone, hard_light_lookup, rs, gs, bs, as);
+					color_tone(pixels[j], tone, rs, gs, bs, as);
 				}
 			}
 		}