evas filter: Implement grayscale filter in SW

Summary: Initial version implementing grayscale filter in SW.

Test Plan:
1. Create filter_example with following.
efl_gfx_filter_program_set(image, "grayscale ()", "grayscale");

1. Run.
./filter_example

Reviewers: Hermet, jsuya

Reviewed By: Hermet

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D10219

src/lib/evas/software_generic/filters/meson.build

@@ -10,6 +10,7 @@ raw_evas_src = [
   'evas_filter_fill.c',
   'evas_filter_mask.c',
   'evas_filter_transform.c',
+  'evas_filter_grayscale.c',
 ]
 
 foreach file : raw_evas_src

src/modules/evas/engines/software_generic/evas_engine.c

@@ -4544,6 +4544,7 @@ _gfx_filter_func_get(Evas_Filter_Command *cmd)
       case EVAS_FILTER_MODE_FILL: func = eng_filter_fill_func_get(cmd); break;
       case EVAS_FILTER_MODE_MASK: func = eng_filter_mask_func_get(cmd); break;
       case EVAS_FILTER_MODE_TRANSFORM: func = eng_filter_transform_func_get(cmd); break;
+      case EVAS_FILTER_MODE_GRAYSCALE: func = eng_filter_grayscale_func_get(cmd); break;
       default: return NULL;
      }
 

src/modules/evas/engines/software_generic/filters/evas_engine_filter.h

@@ -13,5 +13,6 @@ Software_Filter_Func eng_filter_displace_func_get(Evas_Filter_Command *cmd);
 Software_Filter_Func eng_filter_fill_func_get(Evas_Filter_Command *cmd);
 Software_Filter_Func eng_filter_mask_func_get(Evas_Filter_Command *cmd);
 Software_Filter_Func eng_filter_transform_func_get(Evas_Filter_Command *cmd);
+Software_Filter_Func eng_filter_grayscale_func_get(Evas_Filter_Command *cmd);
 
 #endif // EVAS_ENGINE_FILTER_H

src/modules/evas/engines/software_generic/filters/evas_filter_grayscale.c

@@ -0,0 +1,62 @@
+#include "evas_engine_filter.h"
+
+static Eina_Bool
+_evas_filter_grayscale(Evas_Filter_Command *cmd)
+{
+   int sw, sh, dw, dh, x, y, slen, dlen;
+   unsigned int src_len, src_stride, dst_len, dst_stride;
+   Eina_Bool ret = EINA_FALSE;
+   DATA32 *ts, *td, *src = NULL, *dst = NULL;
+   DATA8 r, g, b, gry;
+
+   ector_buffer_size_get(cmd->input->buffer, &sw, &sh);
+   EINA_SAFETY_ON_FALSE_RETURN_VAL((sw > 0) && (sh > 0), ret);
+
+   ector_buffer_size_get(cmd->output->buffer, &dw, &dh);
+   EINA_SAFETY_ON_FALSE_RETURN_VAL((dw > 0) && (dh > 0), ret);
+
+   src = _buffer_map_all(cmd->input->buffer, &src_len, E_READ, E_ARGB, &src_stride);
+   EINA_SAFETY_ON_FALSE_GOTO(src, end);
+
+   dst = _buffer_map_all(cmd->output->buffer, &dst_len, E_WRITE, E_ARGB, &dst_stride);
+   EINA_SAFETY_ON_FALSE_GOTO(dst, end);
+
+   slen = src_stride / sizeof(*src);
+   dlen = dst_stride / sizeof(*dst);
+
+   ts = src;
+   td = dst;
+   for (y = 0; y < sh ; y++)
+     {
+        for (x = 0; x < sw; x++)
+          {
+             A_VAL(td + x) = A_VAL(ts + x);
+             r = R_VAL(ts + x);
+             g = G_VAL(ts + x);
+             b = B_VAL(ts + x);
+
+             /* formula from evas_common_convert_rgba_to_8bpp_gry_256_dith */
+             gry = ((r * 19596) + (g * 38470) + (b * 7472)) >> 16;
+             R_VAL(td + x) = G_VAL(td + x) = B_VAL(td + x) = gry;
+          }
+          ts += slen;
+          td += dlen;
+     }
+
+   ret = EINA_TRUE;
+
+end:
+   if (src) ector_buffer_unmap(cmd->input->buffer, src, src_len);
+   if (dst) ector_buffer_unmap(cmd->output->buffer, dst, dst_len);
+   return ret;
+}
+
+Software_Filter_Func
+eng_filter_grayscale_func_get(Evas_Filter_Command *cmd)
+{
+   EINA_SAFETY_ON_NULL_RETURN_VAL(cmd, NULL);
+   EINA_SAFETY_ON_NULL_RETURN_VAL(cmd->output, NULL);
+   EINA_SAFETY_ON_NULL_RETURN_VAL(cmd->input, NULL);
+
+   return _evas_filter_grayscale;
+}