From 66c2df40c16d2affb9d5024fb9d88afb96f44122 Mon Sep 17 00:00:00 2001
From: Kevin Lange <kevin.lange@dakko.us>
Date: Thu, 13 Sep 2012 23:22:38 -0700
Subject: [PATCH] Fix alpha blending for RGBA destinations.

* Also enable PNG loading in `view`
* Also enable RGBA PNG loading in general
---
 userspace/lib/graphics.c | 37 ++++++++++++++++++++++++++-----------
 userspace/lib/graphics.h |  1 +
 userspace/view.c         | 12 +++++++++++-
 3 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/userspace/lib/graphics.c b/userspace/lib/graphics.c
index c60a2914..a4736026 100644
--- a/userspace/lib/graphics.c
+++ b/userspace/lib/graphics.c
@@ -76,11 +76,12 @@ uint32_t alpha_blend(uint32_t bottom, uint32_t top, uint32_t mask) {
 
 uint32_t alpha_blend_rgba(uint32_t bottom, uint32_t top) {
 	uint8_t a = _ALP(top);
-	uint8_t red = (_RED(bottom) * (255 - a) + _RED(top) * a) / 255;
-	uint8_t gre = (_GRE(bottom) * (255 - a) + _GRE(top) * a) / 255;
-	uint8_t blu = (_BLU(bottom) * (255 - a) + _BLU(top) * a) / 255;
-	uint8_t alp = a + _ALP(bottom) > 255 ? 255 : a + _ALP(bottom);
-	return rgba(red,gre,blu, alp);
+	uint8_t b = ((int)_ALP(bottom) * (255 - a)) / 255;
+	uint8_t alp = a + b;
+	uint8_t red = alp ? (int)(_RED(bottom) * (b) + _RED(top) * a) / (alp): 0;
+	uint8_t gre = alp ? (int)(_GRE(bottom) * (b) + _GRE(top) * a) / (alp): 0;
+	uint8_t blu = alp ? (int)(_BLU(bottom) * (b) + _BLU(top) * a) / (alp): 0;
+	return rgba(red,gre,blu,alp);
 }
 
 void load_sprite(sprite_t * sprite, char * filename) {
@@ -182,13 +183,27 @@ int load_sprite_png(sprite_t * sprite, char * file) {
 	sprite->alpha = 0;
 	sprite->blank = 0;
 
-	printf(">> Notice, loaded with bit_depth = %d\n", bit_depth);
-	for (y = 0; y < height; ++y) {
-		png_byte* row = row_pointers[y];
-		for (x = 0; x < width; ++x) {
-			png_byte * ptr = &(row[x*3]);
-			sprite->bitmap[(y) * width + x] = rgb(ptr[0], ptr[1], ptr[2]);
+	if (color_type == 2) {
+		sprite->alpha = ALPHA_OPAQUE;
+		for (y = 0; y < height; ++y) {
+			png_byte* row = row_pointers[y];
+			for (x = 0; x < width; ++x) {
+				png_byte * ptr = &(row[x*3]);
+				sprite->bitmap[(y) * width + x] = rgb(ptr[0], ptr[1], ptr[2]);
+			}
 		}
+	} else if (color_type == 6) {
+		sprite->alpha = ALPHA_EMBEDDED;
+		for (y = 0; y < height; ++y) {
+			png_byte* row = row_pointers[y];
+			for (x = 0; x < width; ++x) {
+				png_byte * ptr = &(row[x*4]);
+				sprite->bitmap[(y) * width + x] = rgba(ptr[0], ptr[1], ptr[2], ptr[3]);
+			}
+		}
+
+	} else {
+		printf("XXX: UNKNOWN COLOR TYPE: %d!\n", color_type);
 	}
 
 	for (y = 0; y < height; ++y) {
diff --git a/userspace/lib/graphics.h b/userspace/lib/graphics.h
index d7734f35..3e4bbaee 100644
--- a/userspace/lib/graphics.h
+++ b/userspace/lib/graphics.h
@@ -52,6 +52,7 @@ gfx_context_t * init_graphics_fullscreen_double_buffer();
 #define ALPHA_INDEXED  3
 
 uint32_t rgb(uint8_t r, uint8_t g, uint8_t b);
+uint32_t rgba(uint8_t r, uint8_t g, uint8_t b, uint8_t a);
 uint32_t alpha_blend(uint32_t bottom, uint32_t top, uint32_t mask);
 uint32_t alpha_blend_rgba(uint32_t bottom, uint32_t top);
 
diff --git a/userspace/view.c b/userspace/view.c
index c196909f..c29b9e28 100644
--- a/userspace/view.c
+++ b/userspace/view.c
@@ -34,7 +34,12 @@ int main (int argc, char ** argv) {
 	int left = 30;
 	int top  = 30;
 
-	init_sprite(0, argv[1], NULL);
+	if (strstr(argv[1], ".png")) {
+		sprites[0] = malloc(sizeof(sprite_t));
+		load_sprite_png(sprites[0], argv[1]);
+	} else {
+		init_sprite(0, argv[1], NULL);
+	}
 
 	int width  = sprites[0]->width;
 	int height = sprites[0]->height;
@@ -46,6 +51,11 @@ int main (int argc, char ** argv) {
 	ctx = init_graphics_window(wina);
 	draw_fill(ctx, rgb(0,0,0));
 
+	if (sprites[0]->alpha == ALPHA_EMBEDDED) {
+		draw_fill(ctx, rgba(0,0,0,0));
+		window_enable_alpha(wina);
+	}
+
 	draw_sprite(ctx, sprites[0], 0, 0);
 
 	while (1) {