feat(graph): add LCUI_OverPixel()

include/LCUI/graph.h

@@ -133,6 +133,48 @@ LCUI_BEGIN_HEADER
 	(Graph_IsValid(G) && \
 	 ((G)->quote.is_valid ? (G)->quote.is_writable : TRUE))
 
+/*
+ * Pixel over operator with alpha channel
+ * See more: https://en.wikipedia.org/wiki/Alpha_compositing
+ */
+INLINE void LCUI_OverPixel(LCUI_ARGB *dst, const LCUI_ARGB *src)
+{
+	double a, out_a, out_r, out_g, out_b, src_a;
+	/*
+	 * Original formula:
+	 *   Co = (Ca * aa + Cb * ab * (1 - aa)) / (aa + ab * (1 - aa))
+	 *   ao = aa + ab * (1 - aa)
+	 *
+	 * Variable full name:
+	 *   Co => colorOut
+	 *   Ca => colorA
+	 *   Cb => colorB
+	 *   aa => colorA.alpha
+	 *   ab => colorB.alpha
+	 *   ao => colorOut.alpha
+	 *
+	 * The formula used in the code:
+	 *   ai = ab * (1 - aa)
+	 *   Co = (Ca * aa + Cb * ai) / (aa + ai)
+	 *   ao = aa + ai
+	 */
+	src_a = src->a / 255.0;
+	a = (1.0 - src_a) * dst->a / 255.0;
+	out_r = src->r * src_a + dst->r * a;
+	out_g = src->g * src_a + dst->g * a;
+	out_b = src->b * src_a + dst->b * a;
+	out_a = src_a + a;
+	if (out_a > 0) {
+		out_r /= out_a;
+		out_g /= out_a;
+		out_b /= out_a;
+	}
+	dst->r = (unsigned char)(out_r + 0.5);
+	dst->g = (unsigned char)(out_g + 0.5);
+	dst->b = (unsigned char)(out_b + 0.5);
+	dst->a = (unsigned char)(255.0 * out_a + 0.5);
+}
+
 LCUI_API void Graph_PrintInfo(LCUI_Graph *graph);
 
 LCUI_API void Graph_Init(LCUI_Graph *graph);

include/LCUI_Build.h

@@ -1,8 +1,8 @@
 /*
  * LCUI_Build.h -- Build-related configuration definitions
  *
- * Copyright (c) 2018, Liu chao <[email protected]> All rights reserved.
- * 
+ * Copyright (c) 2019, Liu chao <[email protected]> All rights reserved.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
@@ -28,26 +28,23 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
-
 #ifndef LCUI_BUILD_H
 #define LCUI_BUILD_H
 
 #if defined(__GNUC__)
-#  define LCUI_API
-#elif (defined(_MSC_VER) && _MSC_VER < 800) ||\
-    (defined(__BORLANDC__) && __BORLANDC__ < 0x500)
-  /* older Borland and MSC
-   * compilers used '__export' and required this to be after
-   * the type.
-   */
-#  define LCUI_API __export
+#define LCUI_API
 #else /* newer compiler */
-#  ifdef LCUI_EXPORTS
-#    define LCUI_API __declspec(dllexport)
-#  else
-#    define LCUI_API
-#  endif
+#ifdef LCUI_EXPORTS
+#define LCUI_API __declspec(dllexport)
+#else
+#define LCUI_API
+#endif
 #endif /* compiler */
+#if defined(WIN32) && !defined(__cplusplus)
+#define INLINE __inline
+#else
+#define INLINE static inline
+#endif
 
 #ifdef DEBUG
 #define DEBUG_MSG _DEBUG_MSG
@@ -57,7 +54,9 @@
 
 #define LOG Logger_Log
 #define LOGW Logger_LogW
-#define _DEBUG_MSG(format, ...) Logger_Log(__FILE__" %d: %s(): "format, __LINE__, __FUNCTION__,##__VA_ARGS__)
+#define _DEBUG_MSG(format, ...)                                           \
+	Logger_Log(__FILE__ " %d: %s(): " format, __LINE__, __FUNCTION__, \
+		   ##__VA_ARGS__)
 
 #if defined(WIN32) || defined(_WIN32)
 #define LCUI_BUILD_IN_WIN32
@@ -82,10 +81,10 @@
 #endif
 
 #ifdef __cplusplus
-#define LCUI_BEGIN_HEADER  extern "C"{
-#define LCUI_END_HEADER  }
+#define LCUI_BEGIN_HEADER extern "C" {
+#define LCUI_END_HEADER }
 #else
-#define LCUI_BEGIN_HEADER  /* nothing */
+#define LCUI_BEGIN_HEADER /* nothing */
 #define LCUI_END_HEADER
 #endif
 

src/font/fontlibrary.c

@@ -722,33 +722,21 @@ static void FontBitmap_MixARGB(LCUI_Graph *graph, LCUI_Rect *write_rect,
 			       LCUI_Rect *read_rect)
 {
 	int x, y;
+	LCUI_Color tmpColor;
 	LCUI_ARGB *px, *px_row_des;
 	uchar_t *byte_ptr, *byte_row_ptr;
-	double a, ca, out_a, out_r, out_g, out_b, src_a;
+
 	byte_row_ptr = bmp->buffer + read_rect->y * bmp->width;
 	px_row_des = graph->argb + write_rect->y * graph->width;
 	byte_row_ptr += read_rect->x;
 	px_row_des += write_rect->x;
-	ca = color.alpha / 255.0;
 	for (y = 0; y < read_rect->height; ++y) {
 		px = px_row_des;
 		byte_ptr = byte_row_ptr;
 		for (x = 0; x < read_rect->width; ++x, ++byte_ptr, ++px) {
-			src_a = *byte_ptr / 255.0 * ca;
-			a = (1.0 - src_a) * px->a / 255.0;
-			out_r = px->r * a + color.r * src_a;
-			out_g = px->g * a + color.g * src_a;
-			out_b = px->b * a + color.b * src_a;
-			out_a = src_a + a;
-			if (out_a > 0) {
-				out_r /= out_a;
-				out_g /= out_a;
-				out_b /= out_a;
-			}
-			px->r = (uchar_t)(out_r + 0.5);
-			px->g = (uchar_t)(out_g + 0.5);
-			px->b = (uchar_t)(out_b + 0.5);
-			px->a = (uchar_t)(255.0 * out_a + 0.5);
+			tmpColor = color;
+			tmpColor.alpha = *byte_ptr * color.alpha / 255.0;
+			LCUI_OverPixel(px, &tmpColor);
 		}
 		px_row_des += graph->width;
 		byte_row_ptr += bmp->width;