Add canvas, dither, sprites, clock and pixel elements

pixel/sprite.go

@@ -0,0 +1,112 @@
+package pixel
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Sprite is hand-placed art in palette slots, in frames.
+type Sprite struct {
+	W, H   int
+	frames [][]int8
+}
+
+const (
+	cellClear int8 = -1
+	cellInk   int8 = -2
+)
+
+// Art letters naming slots; '.' is clear, '#' the ink.
+const artSlots = "kbflsenwaAigyrcm"
+
+// MustSprite parses string art; blank lines split frames.
+func MustSprite(art string) *Sprite {
+	var frames [][]string
+	var cur []string
+	for _, line := range strings.Split(strings.TrimSpace(art), "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			if cur != nil {
+				frames, cur = append(frames, cur), nil
+			}
+			continue
+		}
+		cur = append(cur, line)
+	}
+	if cur == nil {
+		panic("pixel: empty sprite")
+	}
+	frames = append(frames, cur)
+	sp := &Sprite{W: len(frames[0][0]), H: len(frames[0])}
+	for _, f := range frames {
+		if len(f) != sp.H {
+			panic(fmt.Sprintf("pixel: sprite frames of %d and %d rows", sp.H, len(f)))
+		}
+		px := make([]int8, 0, sp.W*sp.H)
+		for _, row := range f {
+			if len(row) != sp.W {
+				panic(fmt.Sprintf("pixel: sprite row %q is not %d wide", row, sp.W))
+			}
+			for i := range len(row) {
+				px = append(px, cell(row[i]))
+			}
+		}
+		sp.frames = append(sp.frames, px)
+	}
+	return sp
+}
+
+func cell(c byte) int8 {
+	switch c {
+	case '.':
+		return cellClear
+	case '#':
+		return cellInk
+	}
+	if i := strings.IndexByte(artSlots, c); i >= 0 {
+		return int8(i)
+	}
+	panic(fmt.Sprintf("pixel: sprite character %q", c))
+}
+
+func (s *Sprite) Frames() int { return len(s.frames) }
+
+// Mirror returns s flipped left to right.
+func (s *Sprite) Mirror() *Sprite {
+	m := &Sprite{W: s.W, H: s.H}
+	for _, px := range s.frames {
+		out := make([]int8, len(px))
+		for y := range s.H {
+			for x := range s.W {
+				out[y*s.W+x] = px[y*s.W+s.W-1-x]
+			}
+		}
+		m.frames = append(m.frames, out)
+	}
+	return m
+}
+
+// Sprite draws frame of sp; # takes ink; frames wrap.
+func (g Canvas) Sprite(x, y int, sp *Sprite, frame int, ink Slot, scale int) {
+	checkScale(scale)
+	n := len(sp.frames)
+	px := sp.frames[(frame%n+n)%n]
+	for row := range sp.H {
+		line := px[row*sp.W : (row+1)*sp.W]
+		for col := 0; col < sp.W; {
+			v := line[col]
+			end := col + 1
+			for end < sp.W && line[end] == v {
+				end++
+			}
+			if v != cellClear {
+				s := ink
+				if v >= 0 {
+					s = Slot(v)
+				}
+				g.Rect(x+col*scale, y+row*scale, (end-col)*scale, scale, s)
+			}
+			col = end
+		}
+	}
+}