# ../operations/common/brightness-contrast.c

    /* 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 2006 Øyvind Kolås <pippin@gimp.org>
     */

    #include "config.h"
    #include <glib/gi18n-lib.h>

    /* Followed by this #if ... */
    #ifdef GEGL_CHANT_PROPERTIES
    /* ... are the properties of the filter, these are all scalar values
     * (doubles), the the parameters are:
     *       property name,   min,   max, default, "description of property"
     */

    gegl_chant_double_ui (contrast, _("Contrast"), -5.0, 5.0, 1.0, 0.0, 2.0, 1.0,
                       _("Range scale factor"))
    gegl_chant_double_ui (brightness, _("Brightness"), -3.0, 3.0, 0.0, -1.0, 1.0, 1.0,
                       _("Amount to increase brightness"))

    /* this will create the instance structure for our use, and register the
     * property with the given ranges, default values and a comment for the
     * documentation/tooltip.
     */
    #else

    /* Specify the base class we're building our operation on, the base
     * class provides a lot of the legwork so we do not have to. For
     * brightness contrast the best base class is the POINT_FILTER base
     * class.
     */
    #define GEGL_CHANT_TYPE_POINT_FILTER

    /* We specify the file we're in, this is needed to make the code
     * generation for the properties work.
     */
    #define GEGL_CHANT_C_FILE       "brightness-contrast.c"

    /* Including gegl-chant.h creates most of the GObject boiler plate
     * needed, creating a GeglChant instance structure a GeglChantClass
     * structure for our operation, as well as the needed code to register
     * our new gobject with GEGL.
     */
    #include "gegl-chant.h"

    /* prepare() is called on each operation providing data to a node that
     * is requested to provide a rendered result. When prepare is called
     * all properties are known. For brightness contrast we use this
     * opportunity to dictate the formats of the input and output buffers.
     */
    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"));
    }

    /* For GeglOperationPointFilter subclasses, we operate on linear
     * buffers with a pixel count.
     */
    static gboolean
    process (GeglOperation       *op,
             void                *in_buf,
             void                *out_buf,
             glong                n_pixels,
             const GeglRectangle *roi,
             gint                 level)
    {
      /* Retrieve a pointer to GeglChantO structure which contains all the
       * chanted properties
       */
      GeglChantO *o = GEGL_CHANT_PROPERTIES (op);
      gfloat     * GEGL_ALIGNED in_pixel;
      gfloat     * GEGL_ALIGNED out_pixel;
      gfloat      brightness, contrast;
      glong       i;

      in_pixel   = in_buf;
      out_pixel  = out_buf;

      brightness = o->brightness;
      contrast   = o->contrast;

      for (i=0; i<n_pixels; i++)
        {
          out_pixel[0] = (in_pixel[0] - 0.5f) * contrast + brightness + 0.5;
          out_pixel[1] = (in_pixel[1] - 0.5f) * contrast + brightness + 0.5;
          out_pixel[2] = (in_pixel[2] - 0.5f) * contrast + brightness + 0.5;
          out_pixel[3] = in_pixel[3]; /* copy the alpha */
          in_pixel  += 4;
          out_pixel += 4;
        }
      return TRUE;
    }

    #include "opencl/gegl-cl.h"

    static const char* kernel_source =
    "__kernel void kernel_bc(__global const float4     *in,         \n"
    "                        __global       float4     *out,        \n"
    "                        float brightness,                      \n"
    "                        float contrast)                        \n"
    "{                                                              \n"
    "  int gid = get_global_id(0);                                  \n"
    "  float4 in_v  = in[gid];                                      \n"
    "  float4 out_v;                                                \n"
    "  out_v.xyz = (in_v.xyz - 0.5f) * contrast + brightness + 0.5f;\n"
    "  out_v.w   =  in_v.w;                                         \n"
    "  out[gid]  =  out_v;                                          \n"
    "}                                                              \n";

    static gegl_cl_run_data *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,
                int                  level)
    {
      /* Retrieve a pointer to GeglChantO structure which contains all the
       * chanted properties
       */

      GeglChantO *o = GEGL_CHANT_PROPERTIES (op);

      gfloat brightness = o->brightness;
      gfloat contrast   = o->contrast;

      cl_int cl_err = 0;

      if (!cl_data)
        {
          const char *kernel_name[] = {"kernel_bc", 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*)&brightness);
      cl_err |= gegl_clSetKernelArg(cl_data->kernel[0], 3, sizeof(cl_float), (void*)&contrast);
      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;
    }

    /*
     * The class init function sets up information needed for this operations class
     * (template) in the GObject OO framework.
     */
    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);

      /* override the prepare methods of the GeglOperation class */
      operation_class->prepare = prepare;
      /* override the process method of the point filter class (the process methods
       * of our superclasses deal with the handling on their level of abstraction)
       */
      point_filter_class->process = process;
      point_filter_class->cl_process = cl_process;

      /* specify the name this operation is found under in the GUI/when
       * programming/in XML
       */
      operation_class->opencl_support = TRUE;

      gegl_operation_class_set_keys (operation_class,
          "name",       "gegl:brightness-contrast",
          "categories", "color",
          "description", _("Changes the light level and contrast."),
          NULL);
    }

    #endif /* closing #ifdef GEGL_CHANT_PROPERTIES ... else ... */