draw rectangle assumed fixes/fins (untested!)

diff --git a/betty/display.c b/betty/display.c
index 2da19ef..ce8fd7c 100644 (file)
--- 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);