[freetype2] Harmony 11ffff2 2/2: Formulate Harmony LCD rendering.

[Alexei Podtelezhnikov]

branch: Harmony
commit 11ffff2c91e9feca5c90612fec5b2aaa41b4e0e1
Author: Alexei Podtelezhnikov <address@hidden>
Commit: Alexei Podtelezhnikov <address@hidden>

    Formulate Harmony LCD rendering.
    
    This generalizes magic outline shifts that make Harmony LCD
    rendering work in terms of precise two-dimensional RGB subpixel
    positions. These coordinates are now set in time of the `smooth'
    module initialization and later used to shift a glyph outline for
    rendering. FT_RENDER_MODE_LCD and FT_RENDER_MODE_LCD_V use the same
    coordinates. The letter, however, rotates them before using.
    The LCD bitmap padding is also calculated using these coordinates.
    There should be rendering changes resuting from this commit.
---
 include/freetype/internal/ftobjs.h | 26 ++++++++++------
 src/base/ftlcdfil.c                | 50 +++++++++++++++++++++---------
 src/base/ftobjs.c                  |  4 +--
 src/smooth/ftsmooth.c              | 62 ++++++++++++++++++++++++--------------
 4 files changed, 94 insertions(+), 48 deletions(-)

diff --git a/include/freetype/internal/ftobjs.h 
b/include/freetype/internal/ftobjs.h
index 1c3c6ad..9ac05e9 100644
--- a/include/freetype/internal/ftobjs.h
+++ b/include/freetype/internal/ftobjs.h
@@ -312,11 +312,11 @@ FT_BEGIN_HEADER
   FT_CMap_Done( FT_CMap  cmap );
 
 
-  /* adds LCD padding to Min and Max boundaries */
+  /* add LCD padding to CBox */
   FT_BASE( void )
-  ft_lcd_padding( FT_Pos*       Min,
-                  FT_Pos*       Max,
-                  FT_GlyphSlot  slot );
+  ft_lcd_padding( FT_BBox*        cbox,
+                  FT_GlyphSlot    slot,
+                  FT_Render_Mode  mode );
 
 #ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING
 
@@ -392,8 +392,8 @@ FT_BEGIN_HEADER
   /*                                                                       */
   /*    lcd_weights      ::                                                */
   /*    lcd_filter_func  ::                                                */
-  /*      If subpixel rendering is activated, the LCD filtering weights    */
-  /*      and callback function.                                           */
+  /*      These fields specify the LCD filtering weights and callback      */
+  /*      function for ClearType-style subpixel rendering.                 */
   /*                                                                       */
   /*    refcount ::                                                        */
   /*      A counter initialized to~1 at the time an @FT_Face structure is  */
@@ -897,11 +897,15 @@ FT_BEGIN_HEADER
   /*                        interpreter.  Currently, only the TrueType     */
   /*                        bytecode debugger uses this.                   */
   /*                                                                       */
-  /*    lcd_weights      :: If subpixel rendering is activated, the LCD    */
-  /*                        filter weights, if any.                        */
+  /*    lcd_weights      :: The LCD filter weights for ClearType-style     */
+  /*                        subpixel rendering.                            */
   /*                                                                       */
-  /*    lcd_filter_func  :: If subpixel rendering is activated, the LCD    */
-  /*                        filtering callback function.                   */
+  /*    lcd_filter_func  :: The LCD filtering callback function for        */
+  /*                        for ClearType-style subpixel rendering.        */
+  /*                                                                       */
+  /*    lcd_geometry     :: This array specifies LCD subpixel geometry     */
+  /*                        and controls Harmony LCD rendering technique,  */
+  /*                        alternative to ClearType.                      */
   /*                                                                       */
   /*    pic_container    :: Contains global structs and tables, instead    */
   /*                        of defining them globally.                     */
@@ -933,6 +937,8 @@ FT_BEGIN_HEADER
 #ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING
     FT_LcdFiveTapFilter      lcd_weights;      /* filter weights, if any */
     FT_Bitmap_LcdFilterFunc  lcd_filter_func;  /* filtering callback     */
+#else
+    FT_Vector                lcd_geometry[3];  /* RGB subpixel positions */
 #endif
 
 #ifdef FT_CONFIG_OPTION_PIC
diff --git a/src/base/ftlcdfil.c b/src/base/ftlcdfil.c
index 71e7eca..aab04d1 100644
--- a/src/base/ftlcdfil.c
+++ b/src/base/ftlcdfil.c
@@ -34,9 +34,9 @@
 
   /* add padding according to filter weights */
   FT_BASE_DEF (void)
-  ft_lcd_padding( FT_Pos*       Min,
-                  FT_Pos*       Max,
-                  FT_GlyphSlot  slot )
+  ft_lcd_padding( FT_BBox*        cbox,
+                  FT_GlyphSlot    slot,
+                  FT_Render_Mode  mode )
   {
     FT_Byte*                 lcd_weights;
     FT_Bitmap_LcdFilterFunc  lcd_filter_func;
@@ -56,10 +56,20 @@
 
     if ( lcd_filter_func == ft_lcd_filter_fir )
     {
-      *Min -= lcd_weights[0] ? 43 :
-              lcd_weights[1] ? 22 : 0;
-      *Max += lcd_weights[4] ? 43 :
-              lcd_weights[3] ? 22 : 0;
+      if ( mode == FT_RENDER_MODE_LCD )
+      {
+        cbox->xMin -= lcd_weights[0] ? 43 :
+                      lcd_weights[1] ? 22 : 0;
+        cbox->xMax += lcd_weights[4] ? 43 :
+                      lcd_weights[3] ? 22 : 0;
+      }
+      else if ( mode == FT_RENDER_MODE_LCD_V )
+      {
+        cbox->yMin -= lcd_weights[0] ? 43 :
+                      lcd_weights[1] ? 22 : 0;
+        cbox->yMax += lcd_weights[4] ? 43 :
+                      lcd_weights[3] ? 22 : 0;
+      }
     }
   }
 
@@ -343,16 +353,28 @@
 
 #else /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */
 
-  /* add padding according to accommodate outline shifts */
+  /* add padding to accommodate outline shifts */
   FT_BASE_DEF (void)
-  ft_lcd_padding( FT_Pos*       Min,
-                  FT_Pos*       Max,
-                  FT_GlyphSlot  slot )
+  ft_lcd_padding( FT_BBox*        cbox,
+                  FT_GlyphSlot    slot,
+                  FT_Render_Mode  mode )
   {
-    FT_UNUSED( slot );
+    FT_Vector*  sub = slot->library->lcd_geometry;
 
-    *Min -= 21;
-    *Max += 21;
+    if ( mode == FT_RENDER_MODE_LCD )
+    {
+      cbox->xMin -= FT_MAX( FT_MAX( sub[0].x, sub[1].x ), sub[2].x );
+      cbox->xMax -= FT_MIN( FT_MIN( sub[0].x, sub[1].x ), sub[2].x );
+      cbox->yMin -= FT_MAX( FT_MAX( sub[0].y, sub[1].y ), sub[2].y );
+      cbox->yMax -= FT_MIN( FT_MIN( sub[0].y, sub[1].y ), sub[2].y );
+    }
+    else if ( mode == FT_RENDER_MODE_LCD_V )
+    {
+      cbox->xMin -= FT_MAX( FT_MAX( sub[0].y, sub[1].y ), sub[2].y );
+      cbox->xMax -= FT_MIN( FT_MIN( sub[0].y, sub[1].y ), sub[2].y );
+      cbox->yMin += FT_MIN( FT_MIN( sub[0].x, sub[1].x ), sub[2].x );
+      cbox->yMax += FT_MAX( FT_MAX( sub[0].x, sub[1].x ), sub[2].x );
+    }
   }
 
 
diff --git a/src/base/ftobjs.c b/src/base/ftobjs.c
index 8d07e35..642e42f 100644
--- a/src/base/ftobjs.c
+++ b/src/base/ftobjs.c
@@ -403,12 +403,12 @@
 
     case FT_RENDER_MODE_LCD:
       pixel_mode = FT_PIXEL_MODE_LCD;
-      ft_lcd_padding( &cbox.xMin, &cbox.xMax, slot );
+      ft_lcd_padding( &cbox, slot, mode );
       goto Round;
 
     case FT_RENDER_MODE_LCD_V:
       pixel_mode = FT_PIXEL_MODE_LCD_V;
-      ft_lcd_padding( &cbox.yMin, &cbox.yMax, slot );
+      ft_lcd_padding( &cbox, slot, mode );
       goto Round;
 
     case FT_RENDER_MODE_NORMAL:
diff --git a/src/smooth/ftsmooth.c b/src/smooth/ftsmooth.c
index ef176bd..f12e375 100644
--- a/src/smooth/ftsmooth.c
+++ b/src/smooth/ftsmooth.c
@@ -31,6 +31,22 @@
   static FT_Error
   ft_smooth_init( FT_Renderer  render )
   {
+
+#ifndef FT_CONFIG_OPTION_SUBPIXEL_RENDERING
+
+    FT_Vector*  sub = render->root.library->lcd_geometry;
+
+
+    /* set up default subpixel geometry for striped RGB panels. */
+    sub[0].x = -21;
+    sub[0].y = 0;
+    sub[1].x = 0;
+    sub[1].y = 0;
+    sub[2].x = 21;
+    sub[2].y = 0;
+
+#endif
+
     render->clazz->raster_class->raster_reset( render->raster, NULL, 0 );
 
     return 0;
@@ -235,33 +251,33 @@
       unsigned int  width  = bitmap->width;
       int           pitch  = bitmap->pitch;
 
+      FT_Vector*  sub = slot->library->lcd_geometry;
 
-      /* Render 3 separate monochrome bitmaps, shifting the outline  */
-      /* by 1/3 pixel.                                               */
-      width /= 3;
 
-      bitmap->buffer += width;
+      /* Render 3 separate monochrome bitmaps, shifting the outline.  */
+      width /= 3;
 
+      FT_Outline_Translate( outline,           -sub[0].x,           -sub[0].y 
);
       error = render->raster_render( render->raster, &params );
       if ( error )
         goto Exit;
 
-      FT_Outline_Translate( outline, -21, 0 );
-      x_shift        -= 21;
       bitmap->buffer += width;
-
+      FT_Outline_Translate( outline, sub[0].x - sub[1].x, sub[0].y - sub[1].y 
);
       error = render->raster_render( render->raster, &params );
       if ( error )
         goto Exit;
 
-      FT_Outline_Translate( outline,  42, 0 );
-      x_shift        += 42;
-      bitmap->buffer -= 2 * width;
-
+      bitmap->buffer += width;
+      FT_Outline_Translate( outline, sub[1].x - sub[2].x, sub[1].y - sub[2].y 
);
       error = render->raster_render( render->raster, &params );
       if ( error )
         goto Exit;
 
+      x_shift        -= sub[2].x;
+      y_shift        -= sub[2].y;
+      bitmap->buffer -= 2 * width;
+
       /* XXX: Rearrange the bytes according to FT_PIXEL_MODE_LCD.    */
       /* XXX: It is more efficient to render every third byte above. */
 
@@ -286,34 +302,36 @@
     {
       int  pitch  = bitmap->pitch;
 
+      FT_Vector*  sub = slot->library->lcd_geometry;
 
-      /* Render 3 separate monochrome bitmaps, shifting the outline  */
-      /* by 1/3 pixel. Triple the pitch to render on each third row. */
+
+      /* Render 3 separate monochrome bitmaps, shifting the outline. */
+      /* Notice that the subpixel geometry vectors are rotated.      */
+      /* Triple the pitch to render on each third row.               */
       bitmap->pitch *= 3;
       bitmap->rows  /= 3;
 
-      bitmap->buffer += pitch;
-
+      FT_Outline_Translate( outline,           -sub[0].y, sub[0].x            
);
       error = render->raster_render( render->raster, &params );
       if ( error )
         goto Exit;
 
-      FT_Outline_Translate( outline, 0,  21 );
-      y_shift        += 21;
       bitmap->buffer += pitch;
-
+      FT_Outline_Translate( outline, sub[0].y - sub[1].y, sub[1].x - sub[0].x 
);
       error = render->raster_render( render->raster, &params );
       if ( error )
         goto Exit;
 
-      FT_Outline_Translate( outline, 0, -42 );
-      y_shift        -= 42;
-      bitmap->buffer -= 2 * pitch;
-
+      bitmap->buffer += pitch;
+      FT_Outline_Translate( outline, sub[1].y - sub[2].y, sub[2].x - sub[1].x 
);
       error = render->raster_render( render->raster, &params );
       if ( error )
         goto Exit;
 
+      x_shift        -= sub[2].y;
+      y_shift        += sub[2].x;
+      bitmap->buffer -= 2 * pitch;
+
       bitmap->pitch /= 3;
       bitmap->rows  *= 3;
     }