Added font compression example.

src/test/kc/complex/elefont/elefont.kc

@@ -0,0 +1,85 @@
+// Snabel Elefont Compression testing
+
+import "c64"
+import "string"
+
+const byte* SCREEN = 0x0400;
+const byte* ELEFONT = 0x2000;
+const byte* ELEFONT2 = 0x2800;
+byte[0x100] align(0x100) ELEFONT2_MAP;
+
+kickasm(pc ELEFONT, resource "elefont.bin" ) {{
+    .var fontFile = LoadBinary("elefont.bin")
+    .fill fontFile.getSize(), fontFile.get(i)
+}}
+
+void main() {
+    // Compress the font finding identical characters
+    char size = font_compress(ELEFONT, ELEFONT2, ELEFONT2_MAP);
+    // Show compressed font
+    *D018 = toD018(SCREEN, ELEFONT2);
+    // Clear the screen
+    memset(SCREEN, ELEFONT2_MAP[' '], 0x0400);
+    // Show the font
+    char* cursor = SCREEN;
+    char c = 0;
+    for(char y:0..7) {
+        for(char x:0..7) {
+            out(c++, x, y, ELEFONT2_MAP);
+        }
+    }
+}
+
+// Show a 2x2 char on the screen at 2x2-position (x, y) using a font compress mapping
+void out(char c, char x, char y, char* font_mapping) {
+    char* ptr = SCREEN + (unsigned int)y*80 + x*2;
+    ptr[0] = font_mapping[c];
+    ptr[1] = font_mapping[c+0x40];
+    ptr[40] = font_mapping[c+0x80];
+    ptr[41] = font_mapping[c+0xc0];
+}
+
+// Compress a font finding identical characters
+// The compressed font is put into font_compressed and the compress_mapping is updated
+// so that compress_mapping[c] points to the char in font_compressed that is identical to char c in font_original
+// Returns the size of the compressed font (in chars)
+char font_compress(char* font_original, char* font_compressed, char* compress_mapping) {
+    char font_size = 0;
+    char* next_original = font_original;
+    char* next_compressed = font_compressed;
+    for(char i: 0..0xff) {
+        // Look for the char in font_compressed
+        char found = font_find(next_original, font_compressed, font_size);
+        if(found==0xff) {
+            // Glyph not found - create it
+            for(char l:0..7)
+                next_compressed[l] = next_original[l];
+            next_compressed += 8;
+            found = font_size;
+            font_size++;
+        }
+        compress_mapping[i] = found;
+        next_original += 8;
+    }
+    return font_size;
+}
+
+// Look for a glyph within a font
+// Only looks at the first font_size glyphs
+// Returns the index of the glyph within the font. Returns 0xff if the glyph is not found.
+char font_find(char* glyph, char* font, char font_size) {
+    for(char i=0;i<font_size;i++) {
+        char found = 1;
+        for(char l:0..7) {
+            if(glyph[l]!=font[l]) {
+                found = 0;
+                break;
+            }
+        }
+        if(found)
+            return i;
+        font += 8;
+    }
+    // Not found
+    return 0xff;
+}