1 files changed, 243 insertions, 0 deletions
diff --git a/src/im_colorhsi.cpp b/src/im_colorhsi.cpp
new file mode 100644
index 0000000..3852527
--- /dev/null
+++ b/src/im_colorhsi.cpp
@@ -0,0 +1,243 @@
+/** \file
+ * \brief HSI Color Manipulation
+ *
+ * See Copyright Notice in im_lib.h
+ * $Id: im_colorhsi.cpp,v 1.1 2008/10/17 06:10:16 scuri Exp $
+ */
+
+
+#include <math.h>
+
+#include "im_colorhsi.h"
+#include "im_color.h"
+
+static const float rad60 =  1.0471975f;
+static const float rad120 = 2.0943951f;
+static const float rad180 = 3.1415926f;
+static const float rad240 = 4.1887902f;
+static const float rad300 = 5.2359877f;
+static const float rad360 = 6.2831853f;
+static const float sqrt3 = 1.7320508f;
+
+/**********************************/               
+/*         HSI MAX S              */
+/**********************************/               
+               
+static void iSmax01(float h, float hr, float hb, float hg, float *h0, float *h1)
+{
+  if (h < rad60)
+  {
+    *h0 = hb;
+    *h1 = hr;
+  }
+  else if (h < rad120)
+  {
+    *h0 = hb;
+    *h1 = hg;
+  }
+  else if (h < rad180)
+  {
+    *h0 = hr;
+    *h1 = hg;
+  }
+  else if (h < rad240)
+  {
+    *h0 = hr;
+    *h1 = hb;
+  }
+  else if (h < rad300)
+  {
+    *h0 = hg;
+    *h1 = hb;
+  }
+  else
+  {
+    *h0 = hg;
+    *h1 = hr;
+  }
+}
+
+float imColorHSI_Smax(float h, double cosh, double sinh, float i)
+{
+  float hr, hb, hg, imax, h0, h1;
+
+  if (i == 0 || i == 1)
+    return 0.0f;
+
+  if (i == 1.0f/3.0f || i == 2.0f/3.0f)
+    return 1.0f;
+
+  hr = (float)(cosh / 1.5);
+  hg = (float)((-cosh + sinh*sqrt3)/ 3.0);
+  hb = (float)((-cosh - sinh*sqrt3)/ 3.0);
+
+  /* at bottom */
+  if (i < 1.0f/3.0f)
+  {
+    /* face B=0 */
+    if (h < rad120)
+      return -i/hb;
+
+    /* face R=0 */
+    if (h < rad240)
+      return -i/hr;
+
+    /* face G=0 */
+    return -i/hg;
+  }
+
+  /* at top */
+  if (i > 2.0f/3.0f)
+  {
+    /* face R=1 */
+    if (h < rad60 || h > rad300)
+      return (1-i)/hr;
+
+    /* face G=1 */
+    if (h < rad180)
+      return (1-i)/hg;
+
+    /* face B=1 */
+    return (1-i)/hb;
+  }
+
+  /* in the middle */
+
+  iSmax01(h, hr, hb, hg, &h0, &h1);
+
+  if (h == 0 || h == rad120 || h == rad240)
+    imax = 1.0f/3.0f;
+  else if (h == rad60 || h == rad180 || h == rad300)
+    imax = 2.0f/3.0f;
+  else
+    imax = h0 / (h0 - h1);
+
+  if (i < imax) 
+    return -i/h0;
+  else
+    return (1-i)/h1;
+}
+
+float imColorHSI_ImaxS(float h, double cosh, double sinh)
+{
+  float i, h0, h1;
+  float hr, hb, hg;
+
+  if (h == 0 || h == rad120 || h == rad240)
+    return 1.0f/3.0f;
+
+  if (h == rad60 || h == rad180 || h == rad300)
+    return 2.0f/3.0f;
+
+  hr = (float)(cosh / 1.5f);
+  hg = (float)((-cosh + sinh*sqrt3)/ 3.0);
+  hb = (float)((-cosh - sinh*sqrt3)/ 3.0);
+
+  iSmax01(h, hr, hb, hg, &h0, &h1);
+
+  i = h0 / (h0 - h1);
+
+  return i;
+}
+
+/**********************************/               
+/*         RGB 2 HSI              */
+/**********************************/               
+
+void imColorRGB2HSI(float r, float g, float b, float *h, float *s, float *i)
+{            
+  float v, u;
+  double H;
+
+  v = r - (g + b)/2;
+  u = (g - b) * (sqrt3/2);
+
+  *i = (r + g + b)/3;
+  *s = (float)sqrt(v*v + u*u);
+  
+  if (*s == 0)
+    *h = 360.0f;  /* by definition */
+  else
+  {
+    H = atan2(u, v);
+    if (H < 0.0f) H += rad360;
+    *h = (float)(H * 57.2957795131);
+  }
+}
+
+void imColorRGB2HSIbyte(unsigned char r, unsigned char g, unsigned char b, float *h, float *s, float *i)
+{
+  float fr = imColorReconstruct(r, (imbyte)255);
+  float fg = imColorReconstruct(g, (imbyte)255);
+  float fb = imColorReconstruct(b, (imbyte)255);
+  
+  imColorRGB2HSI(fr, fg, fb, h, s, i);
+}
+
+/**********************************/               
+/*         HSI 2 RGB              */
+/**********************************/               
+
+void imColorHSI2RGB(float h, float s, float i, float *r, float *g, float *b)
+{
+  static int first = 1;
+  static double _sqrt3;
+  double cosh, sinh, H, v, u;
+
+  if (first)
+  {
+    _sqrt3 = sqrt(3.0);
+    first = 0;
+  }
+
+  if (s == 0.0f || i == 1.0f || i == 0.0f || (int)h == 360)
+  {
+    *r = i;
+    *g = i;
+    *b = i;
+    return;
+  }
+
+  if (i < 0) i = 0;
+  if (i > 1) i = 1;
+
+  if (h > 360)  h = (float)fmod(h, 360);
+  if (h < 0.0f) h += 360;
+
+  H = h / 57.2957795131;
+
+  cosh = cos(H);
+  sinh = sin(H);
+    
+  {
+    float smax = imColorHSI_Smax((float)H, cosh, sinh, i);
+    if (s < 0) s = 0;
+    if (s > smax) s = smax;
+  }
+
+  v = s * cosh;
+  u = s * sinh * _sqrt3;
+
+  *r = (float)(i + v/1.5);
+  *g = (float)(i - (v - u)/3.0);
+  *b = (float)(i - (v + u)/3.0);
+
+  if (*r < 0) *r = -*r;
+  if (*g < 0) *g = -*g;
+  if (*b < 0) *b = -*b;
+
+  if (*r > 1) *r = 1.0f;
+  if (*g > 1) *g = 1.0f;
+  if (*b > 1) *b = 1.0f;
+}
+
+void imColorHSI2RGBbyte(float h, float s, float i, unsigned char *r, unsigned char *g, unsigned char *b)
+{
+  float fr, fg, fb;
+  
+  imColorHSI2RGB(h, s, i, &fr, &fg, &fb);
+  
+  *r = imColorQuantize(fr, (imbyte)255);
+  *g = imColorQuantize(fg, (imbyte)255);
+  *b = imColorQuantize(fb, (imbyte)255);
+}