Merge pull request #76 from jdgleaver/post-processing

Add optional colour correction + interframe blending

2 files changed, 147 insertions, 0 deletions

diff --git a/tools/Makefile b/tools/Makefile
new file mode 100644
index 0000000..91dc1aa
--- /dev/null
+++ b/tools/Makefile
@@ -0,0 +1,12 @@
+CC = gcc
+CFLAGS  = -Wall
+
+TARGET = generate_cc_lut
+
+all: $(TARGET)
+
+$(TARGET): $(TARGET).c
+	$(CC) $(CFLAGS) -o $(TARGET) $(TARGET).c -lm
+
+clean:
+	$(RM) $(TARGET)
diff --git a/tools/generate_cc_lut.c b/tools/generate_cc_lut.c
new file mode 100644
index 0000000..33b4cef
--- /dev/null
+++ b/tools/generate_cc_lut.c
@@ -0,0 +1,135 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <math.h>
+
+/* gpsp targets devices that are too slow to generate
+ * a colour correction table at runtime. We therefore
+ * have to pre-generate the lookup table array... */
+
+/* Colour correction defines */
+#define CC_TARGET_GAMMA   2.2f
+#define CC_RGB_MAX       31.0f
+#define CC_LUM            0.94f
+#define CC_R              0.82f
+#define CC_G              0.665f
+#define CC_B              0.73f
+#define CC_RG             0.125f
+#define CC_RB             0.195f
+#define CC_GR             0.24f
+#define CC_GB             0.075f
+#define CC_BR            -0.06f
+#define CC_BG             0.21f
+#define CC_GAMMA_ADJ      1.0f
+
+/* Output video is RGB565. This is 16bit,
+ * but only 15 bits are actually used
+ * (i.e. 'G' is the highest 5 bits of the
+ * 6bit component). To save memory, we
+ * only include 15bit compound values
+ * and convert RGB565 video to 15bit when
+ * using the lookup table */
+#define CC_LUT_SIZE       32768
+
+static uint16_t c_lut[CC_LUT_SIZE] = {0};
+
+void init_lut(void)
+{
+   size_t color;
+   float display_gamma_inv = 1.0f / CC_TARGET_GAMMA;
+   float rgb_max_inv       = 1.0f / CC_RGB_MAX;
+   float adjusted_gamma    = CC_TARGET_GAMMA + CC_GAMMA_ADJ;
+
+   /* Populate colour correction look-up table */
+   for (color = 0; color < CC_LUT_SIZE; color++)
+   {
+      unsigned r_final = 0;
+      unsigned g_final = 0;
+      unsigned b_final = 0;
+      /* Extract values from RGB555 input */
+      const unsigned r = color >> 10 & 0x1F;
+      const unsigned g = color >>  5 & 0x1F;
+      const unsigned b = color       & 0x1F;
+      /* Perform gamma expansion */
+      float r_float = pow((float)r * rgb_max_inv, adjusted_gamma);
+      float g_float = pow((float)g * rgb_max_inv, adjusted_gamma);
+      float b_float = pow((float)b * rgb_max_inv, adjusted_gamma);
+      /* Perform colour mangling */
+      float r_correct = CC_LUM * ((CC_R  * r_float) + (CC_GR * g_float) + (CC_BR * b_float));
+      float g_correct = CC_LUM * ((CC_RG * r_float) + (CC_G  * g_float) + (CC_BG * b_float));
+      float b_correct = CC_LUM * ((CC_RB * r_float) + (CC_GB * g_float) + (CC_B  * b_float));
+      /* Range check... */
+      r_correct = r_correct > 0.0f ? r_correct : 0.0f;
+      g_correct = g_correct > 0.0f ? g_correct : 0.0f;
+      b_correct = b_correct > 0.0f ? b_correct : 0.0f;
+      /* Perform gamma compression */
+      r_correct = pow(r_correct, display_gamma_inv);
+      g_correct = pow(g_correct, display_gamma_inv);
+      b_correct = pow(b_correct, display_gamma_inv);
+      /* Range check... */
+      r_correct = r_correct > 1.0f ? 1.0f : r_correct;
+      g_correct = g_correct > 1.0f ? 1.0f : g_correct;
+      b_correct = b_correct > 1.0f ? 1.0f : b_correct;
+      /* Convert to RGB565 */
+      r_final = (unsigned)((r_correct * CC_RGB_MAX) + 0.5f) & 0x1F;
+      g_final = (unsigned)((g_correct * CC_RGB_MAX) + 0.5f) & 0x1F;
+      b_final = (unsigned)((b_correct * CC_RGB_MAX) + 0.5f) & 0x1F;
+      c_lut[color] = r_final << 11 | g_final << 6 | b_final;
+   }
+}
+
+int main(int argc, char *argv[])
+{
+   FILE *file = NULL;
+   size_t i;
+
+   /* Populate lookup table */
+   init_lut();
+
+   /* Write header file */
+   file = fopen("../gba_cc_lut.h", "w");
+
+   if (!file)
+      return 1;
+
+   fprintf(file,
+         "#ifndef __CC_LUT_H__\n"
+         "#define __CC_LUT_H__\n\n"
+         "#include \"common.h\"\n\n"
+         "extern const u16 gba_cc_lut[];\n\n"
+         "#endif /* __CC_LUT_H__ */\n");
+
+   fclose(file);
+   file = NULL;
+
+   /* Write source file */
+   file = fopen("../gba_cc_lut.c", "w");
+
+   if (!file)
+      return 1;
+
+   fprintf(file,
+         "#include \"gba_cc_lut.h\"\n\n"
+         "const u16 gba_cc_lut[] = {\n");
+
+   for (i = 0; i < CC_LUT_SIZE; i++)
+   {
+      fprintf(file, " 0x%04x", c_lut[i]);
+
+      if (i == CC_LUT_SIZE - 1)
+         fprintf(file, "\n");
+      else
+      {
+         if ((i + 1) % 5 == 0)
+            fprintf(file, ",\n");
+         else
+            fprintf(file, ",");
+      }
+   }
+
+   fprintf(file, "};\n");
+
+   fclose(file);
+   file = NULL;
+
+   return 0;
+}