From 71bf7666ce24cd3c07bb16648e0ab231e07be6d8 Mon Sep 17 00:00:00 2001
From: hackbard <hackbard@sage.physik.uni-augsburg.de>
Date: Fri, 14 Sep 2007 12:36:07 +0200
Subject: [PATCH] draw rectangle assumed fixes/fins (untested!)

---
 betty/display.c | 85 ++++++++++++++++++++++++++-----------------------
 1 file changed, 45 insertions(+), 40 deletions(-)

diff --git a/betty/display.c b/betty/display.c
index 2da19ef..ce8fd7c 100644
--- a/betty/display.c
+++ b/betty/display.c
@@ -7,9 +7,13 @@
 
 /*
  * some comments on alpha blending!
+ * ################################
  *
- * ...
- *
+ * if c is the result of layer a over layer b with opacity alpha:
+ * 
+ * c=alpha*a+(1-alpha)*b and if alpha is a byte (0-255)
+ * => c=alpha*a+(255-alpha)*b
+ * 
  */
 
 #include "display.h"
@@ -104,54 +108,55 @@ void display_load_logo(u8 *src) {
 	}
 }
 
-void display_draw_rectangle(int x,int y,int w,int h,u8 fill,u8 alpha) {
+#define display_m2i(m,r) (((((m)[0]>>r)&1)<<1)|(((m)[1]>>r)&1))
 
-	int c,r,rmax;
-	u8 p,spage,epage;
-	u8 b[2],a[2];		// c = a over b => c=alpha*a+(1-alpha)*b
+void display_draw_rectangle(u8 x,u8 y,u8 w,u8 h,u8 fill,u8 alpha) {
 
-	a[0]=0;
-	a[1]=0;
-	switch(fill) {
-		case DISPLAY_FILL_LG:
-			a[1]=1;
-			break;
-		case DISPLAY_FILL_DG:
-			a[0]=1;
-			break;
-		case DISPLAY_FILL_B:
-			a[0]=1;
-			a[1]=1;
-		case DISPLAY_FILL_W:
-		default:
-			break;
-	}
+	u8 page,col,row,rmax,cnt;
+	u8 d[2];
+	int ca,cb;
+	u8 a,b,c;			// c = a over b
+
+	a=fill&0x03;
+	ca=0;
+	for(cnt=0;cnt<a;cnt++)		// contribution of a: alpha*a
+		ca+=alpha;
 
-	spage=y>>3;					// start page = y/8
-	epage=(y+h)>>3;					// end page (y+h)/8
-
-	for(p=spage;p<=epage;p++) {
-		DISPLAY_SET_PAGE_ADDR(p);
-		for(c=x;c<x+w;c++) {
-			DISPLAY_SET_C_ADDR(c);
-			b[0]=DISPLAY_DATA;		// dummy read (p.16)
-			b[0]=DISPLAY_DATA;
-			b[1]=DISPLAY_DATA;
-			rmax=y+8>y+h?y+h:y+8;
-			for(r=y;r<rmax;r++) {
-				b[0]&=~(1<<r);
-				b[1]&=~(1<<r);
-				b[0]|=a[0]<<r;
-				b[1]|=a[1]<<r;
+	for(page=(y>>3);page<=((y+h)>>3);page++) {	// page = y/8
+		DISPLAY_SET_PAGE_ADDR(page);
+		rmax=(page+1)<<3;			// row max
+		if(rmax>y+h)
+			rmax=y+h;
+		for(col=x;col<x+w;col++) {
+			DISPLAY_SET_C_ADDR(col);
+			d[0]=DISPLAY_DATA;		// dummy read (p.16)
+			d[0]=DISPLAY_DATA;
+			d[1]=DISPLAY_DATA;
+			for(row=y;row<rmax;row++) {
+				// contribution of b: (255-alpha)*b
+				b=display_m2i(d,row);
+				cb=0;
+				for(cnt=0;cnt<b;cnt++)
+					cb+=(255-alpha);
+				// finally there is c
+				c=(ca+cb)>>8;
+				d[0]&=~(1<<row);
+				d[1]&=~(1<<row);
+				d[0]|=((c>>1)&1)<<row;
+				d[1]|=(c&1)<<row;
 			}
-			DISPLAY_SET_C_ADDR(c);
+			DISPLAY_SET_C_ADDR(col);
 			DISPLAY_DATA=b[0];
 			DISPLAY_DATA=b[1];
 		}
-		y+=8;
+		y=rmax;
 	}
 }
 
+void display_draw_buf(u8 x,u8 y,u8 w,u8 h,u8 *buf,u8 alpha) {
+
+}
+
 void display_bl_init(void) {
 
 	IODIR0|=(1<<4);
-- 
2.20.1