[gegl] operations: add exposure operation

[Ãyvind KolÃs <ok src gnome org>]

commit 6b739f1948c2082750d054959e2ac9c24ead1518
Author: Felix Ulber <felix ulber gmx de>
Date:   Fri Dec 21 16:50:42 2012 +0100

    operations: add exposure operation
    
    This operation is usefull for manipulating an images contrast and brigness in a different way to the classical brightness/contrast. It hast three parameters, applied in the following order: a multiplier, working in a relative logarithmic way, an offset and a gamma correction. This is most important when working with high dynamic range images.
    
    Referring to bug:
    https://bugzilla.gnome.org/show_bug.cgi?id=690615

 operations/common/exposure.c |  182 ++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 182 insertions(+), 0 deletions(-)
---
diff --git a/operations/common/exposure.c b/operations/common/exposure.c
new file mode 100644
index 0000000..fdac232
--- /dev/null
+++ b/operations/common/exposure.c
@@ -0,0 +1,182 @@
+/* This file is an image processing operation for GEGL
+ *
+ * GEGL is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * GEGL is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with GEGL; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2012 Felix Ulber <felix ulber gmx de>
+ */
+
+
+#include "config.h"
+#include <glib/gi18n-lib.h>
+
+
+#ifdef GEGL_CHANT_PROPERTIES
+gegl_chant_double_ui (exposure, _("Exposure"), -G_MAXDOUBLE, G_MAXDOUBLE, 0.0, -10.0, 10.0, 1.0,
+                   _("Relative brightness change in stops"))
+gegl_chant_double_ui (offset, _("Offset"), -0.5, 0.5, 0.0, -0.5, 0.5, 1.0,
+                   _("Offset value added"))
+gegl_chant_double_ui (gamma, _("Gamma"), 0.01, 10, 1.0, 0.01, 3.0, 1.0,
+                   _("Gamma correction"))
+#else
+
+#define GEGL_CHANT_TYPE_POINT_FILTER
+#define GEGL_CHANT_C_FILE         "exposure.c"
+
+#include "gegl-chant.h"
+
+#include <math.h>
+#ifdef _MSC_VER
+#define powf(a,b) ((gfloat)pow(a,b))
+#endif
+
+static void prepare (GeglOperation *operation)
+{
+  gegl_operation_set_format (operation, "input", babl_format ("RGBA float"));
+  gegl_operation_set_format (operation, "output", babl_format ("RGBA float"));
+}
+
+/* GeglOperationPointFilter gives us a linear buffer to operate on
+ * in our requested pixel format
+ */
+static gboolean
+process (GeglOperation       *op,
+         void                *in_buf,
+         void                *out_buf,
+         glong                n_pixels,
+         const GeglRectangle *roi,
+         gint                 level)
+{
+  GeglChantO *o = GEGL_CHANT_PROPERTIES (op);
+  gfloat     *in_pixel;
+  gfloat     *out_pixel;
+
+  gfloat      gain = powf(2.0, o->exposure);
+  gfloat      offset = o->offset;
+  gfloat      gamma = 1.0 / o->gamma;
+  
+  glong       i;
+
+  in_pixel = in_buf;
+  out_pixel = out_buf;
+  
+  for (i=0; i<n_pixels; i++)
+    {
+      float c[3];
+      c[0] = (in_pixel[0] * gain + offset);
+      c[1] = (in_pixel[1] * gain + offset);
+      c[2] = (in_pixel[2] * gain + offset);
+      
+      // ???
+      c[0] = fmaxf(0.0, c[0]);
+      c[1] = fmaxf(0.0, c[1]);
+      c[2] = fmaxf(0.0, c[2]);
+      
+      out_pixel[0] = powf(c[0], gamma);
+      out_pixel[1] = powf(c[1], gamma);
+      out_pixel[2] = powf(c[2], gamma);
+      
+      out_pixel[3] = in_pixel[3];
+      
+      out_pixel += 4;
+      in_pixel += 4;
+    }
+    
+  return TRUE;
+}
+
+#include "opencl/gegl-cl.h"
+
+static const char* kernel_source =
+"__kernel void kernel_exposure(__global const float4     *in,      \n"
+"                            __global       float4     *out,     \n"
+"                            float gain,                          \n"
+"                            float offset,                       \n"
+"                            float gamma)                        \n"
+"{                                                               \n"
+"  int gid = get_global_id(0);                                   \n"
+"  float4 in_v  = in[gid];                                       \n"
+"  float4 out_v;                                                 \n"
+"  out_v.xyz = pow(max((in_v.xyz * gain) + offset, 0.0), 1.0/gamma); \n"
+"  out_v.w   =  in_v.w;                                          \n"
+"  out[gid]  =  out_v;                                           \n"
+"}                                                               \n";
+
+static GeglClRunData *cl_data = NULL;
+
+/* OpenCL processing function */
+static cl_int
+cl_process (GeglOperation       *op,
+            cl_mem               in_tex,
+            cl_mem               out_tex,
+            size_t               global_worksize,
+            const GeglRectangle *roi,
+            gint                 level)
+{
+  /* Retrieve a pointer to GeglChantO structure which contains all the
+   * chanted properties
+   */
+
+  GeglChantO *o = GEGL_CHANT_PROPERTIES (op);
+
+  gfloat      gain = powf(2.0, o->exposure);
+  gfloat      offset = o->offset;
+  gfloat      gamma = 1.0 / o->gamma;
+  
+  cl_int cl_err = 0;
+
+  if (!cl_data)
+    {
+      const char *kernel_name[] = {"kernel_exposure", NULL};
+      cl_data = gegl_cl_compile_and_build (kernel_source, kernel_name);
+    }
+  if (!cl_data) return 1;
+
+  cl_err |= gegl_clSetKernelArg(cl_data->kernel[0], 0, sizeof(cl_mem),   (void*)&in_tex);
+  cl_err |= gegl_clSetKernelArg(cl_data->kernel[0], 1, sizeof(cl_mem),   (void*)&out_tex);
+  cl_err |= gegl_clSetKernelArg(cl_data->kernel[0], 2, sizeof(cl_float), (void*)&gain);
+  cl_err |= gegl_clSetKernelArg(cl_data->kernel[0], 3, sizeof(cl_float), (void*)&offset);
+  cl_err |= gegl_clSetKernelArg(cl_data->kernel[0], 4, sizeof(cl_float), (void*)&gamma);
+  if (cl_err != CL_SUCCESS) return cl_err;
+
+  cl_err = gegl_clEnqueueNDRangeKernel(gegl_cl_get_command_queue (),
+                                        cl_data->kernel[0], 1,
+                                        NULL, &global_worksize, NULL,
+                                        0, NULL, NULL);
+  if (cl_err != CL_SUCCESS) return cl_err;
+
+  return cl_err;
+}
+
+static void
+gegl_chant_class_init (GeglChantClass *klass)
+{
+  GeglOperationClass            *operation_class;
+  GeglOperationPointFilterClass *point_filter_class;
+
+  operation_class    = GEGL_OPERATION_CLASS (klass);
+  point_filter_class = GEGL_OPERATION_POINT_FILTER_CLASS (klass);
+
+  point_filter_class->process = process;
+  point_filter_class->cl_process = cl_process;
+
+  operation_class->opencl_support = TRUE;
+
+  gegl_operation_class_set_keys (operation_class,
+    "name"       , "gegl:exposure",
+    "categories" , "color",
+    "description", _("Changes Exposure and Contrast, mainly for use with high dynamic range images."),
+    NULL);
+}
+
+#endif