Expose functions for gamma correction

2 files changed, 38 insertions, 2 deletions

diff --git a/include/swgfx.h b/include/swgfx.h
index e9e69b8..9c3361d 100644
--- a/include/swgfx.h
+++ b/include/swgfx.h
@@ -72,7 +72,8 @@ void   sgDel(swgfx**);
 
 // TODO: Write client app first, then implement the functions below in the C file.
 
-void sgPresent(swgfx*, sgVec2i dimensions, sgScreenPixel* screen);
+sgPixel* sgColourBuffer(swgfx*);
+void     sgPresent(swgfx*, sgVec2i dimensions, sgScreenPixel* screen);
 
 void sgModelId    (swgfx*);
 void sgModel      (swgfx*, sgVec3 position, sgVec3 right, sgVec3 up, sgVec3 forward);
@@ -94,4 +95,7 @@ void sgTriangleStrip (swgfx*, size_t count, const sgVec3*, const sgNormal*);
 void sgTrianglesIndexed(swgfx*, size_t numIndices, const sgIdx* indices, const sgVec3* positions, const sgVec2* texcoords);
 void sgTrianglesIndexedNonUniform(swgfx*, size_t numTris, const sgTriIdx* tris, const sgVec3* positions, const sgVec2* texcoords);
 
+void sgGamma   (swgfx*, sgPixel*, int width, int height);
+void sgGammaInv(swgfx*, sgPixel*, int width, int height);
+
 void sgCheck(swgfx*);
diff --git a/src/swgfx.c b/src/swgfx.c
index 153a5f4..bbf9a5b 100644
--- a/src/swgfx.c
+++ b/src/swgfx.c
@@ -78,6 +78,7 @@ static inline sgVec3 neg3(sgVec3 v) { return (sgVec3){-v.x, -v.y, -v.z}; }
 static inline sgVec3 sub3(sgVec3 a, sgVec3 b) { return (sgVec3){a.x - b.x, a.y - b.y, a.z - b.z}; }
 static inline sgVec3 div3(sgVec3 a, sgVec3 b) { return (sgVec3){a.x / b.x, a.y / b.y, a.z / b.z}; }
 static inline sgVec3 scale3(sgVec3 v, R s) { return (sgVec3){v.x * s, v.y * s, v.z * s}; }
+static inline sgVec3 exp3(sgVec3 v, R exp) { return (sgVec3){powf(v.x, exp), powf(v.y, exp), powf(v.z, exp)};}
 static inline R dot3(sgVec3 a, sgVec3 b) { return a.x * b.x + a.y * b.y + a.z * b.z; }
 static inline R normsq3(sgVec3 v) { return v.x * v.x + v.y * v.y + v.z * v.z; }
 static inline R norm3  (sgVec3 v) { return (R)sqrt(normsq3(v)); }
@@ -268,11 +269,17 @@ static inline sgMat4 Mat4Perspective(R fovy, R aspect, R near, R far) {
     0,          0,                -1,                   0);
 }
 
+static inline sgVec3 PixelToVec3(sgPixel p) {
+  return (sgVec3){(R)p.r / 255.f, (R)p.g / 255.f, (R)p.b / 255.f};
+}
+static inline sgPixel Vec3ToPixel(sgVec3 p, R a) {
+  return (sgPixel){(uint8_t)(p.x * 255.f), (uint8_t)(p.y * 255.f), (uint8_t)(p.z * 255.f), (uint8_t)(a * 255.f)};
+}
 static inline sgVec4 PixelToVec4(sgPixel p) {
   return (sgVec4){(R)p.r / 255.f, (R)p.g / 255.f, (R)p.b / 255.f, (R)p.a / 255.f};
 }
 static inline sgPixel Vec4ToPixel(sgVec4 p) {
-  return (sgPixel){(int)(p.x * 255.f), (int)(p.y * 255.f), (int)(p.z * 255.f), (int)(p.w * 255.f)};
+  return (sgPixel){(uint8_t)(p.x * 255.f), (uint8_t)(p.y * 255.f), (uint8_t)(p.z * 255.f), (uint8_t)(p.w * 255.f)};
 }
 
 #ifndef _NDEBUG
@@ -729,6 +736,11 @@ void sgDel(swgfx** ppSwgfx) {
   }
 }
 
+sgPixel* sgColourBuffer(swgfx* gfx) {
+  assert(gfx);
+  return gfx->colour;
+}
+
 void sgPresent(swgfx* gfx, sgVec2i dimensions, sgScreenPixel* screen) {
   assert(gfx);
   assert(screen);
@@ -891,6 +903,26 @@ void sgTrianglesIndexedNonUniform(swgfx* gfx, size_t numTris, const sgTriIdx* tr
   }
 }
 
+static void ImageExp(sgPixel* pixels, int width, int height, R exp) {
+  assert(pixels);
+  for (int i = 0; i < width * height; ++i) {
+    sgPixel* p = &pixels[i];
+    *p = Vec3ToPixel(exp3(PixelToVec3(*p), exp), p->a);
+  }
+}
+
+void sgGamma(swgfx* gfx, sgPixel* pixels, int width, int height) {
+  assert(gfx);
+  assert(pixels);
+  ImageExp(pixels, width, height, 2.2f);
+}
+
+void sgGammaInv(swgfx* gfx, sgPixel* pixels, int width, int height) {
+  assert(gfx);
+  assert(pixels);
+  ImageExp(pixels, width, height, 1.0f/2.2f);
+}
+
 static bool ViewportWithinBuffer(swgfx* gfx) {
   assert(gfx);
   const sgViewport_t vp = gfx->viewport;