Add EAN barcodes.

src/bar_code.toit

@@ -2,6 +2,12 @@
 // Use of this source code is governed by an MIT-style license that can be
 // found in the LICENSE file.
 
+import font show Font
+
+import .common
+import .element show CustomElement
+import .style
+
 EAN_13_QUIET_ZONE_WIDTH ::= 9
 EAN_13_START_WIDTH ::= 3
 EAN_13_MIDDLE_WIDTH ::= 5
@@ -15,3 +21,110 @@ EAN_13_L_CODES_ ::= [0x0d, 0x19, 0x13, 0x3d, 0x23, 0x31, 0x2f, 0x3b, 0x37, 0x0b]
 EAN_13_G_CODES_ ::= [0x27, 0x33, 0x1b, 0x21, 0x1d, 0x39, 0x05, 0x11, 0x09, 0x17]
 // Encoding of the first (invisible) digit.
 EAN_13_FIRST_CODES_ ::= [0x00, 0x0b, 0x0d, 0x0e, 0x13, 0x19, 0x1c, 0x15, 0x16, 0x1a]
+
+// Element that draws a standard EAN-13 bar code.  TODO: Other scales.
+class BarCodeEanElement extends CustomElement:
+  color_/int? := 0
+  background_ := 0xff
+  sans10_ ::= Font.get "sans10"
+  number_height_ := EAN_13_BOTTOM_SPACE
+
+  type -> string: return "bar-code-ean"
+
+  set_attribute key/string value -> none:
+    if key == "color":
+      if color_ != value:
+        invalidate
+        color_ = value
+    else:
+      super key value
+
+  code_/string := ?  // 13 digit code as a string.
+
+  code= value/string -> none:
+    if value != code_: invalidate
+    code_ = value
+
+  code -> string: return code_
+
+  /**
+  $code_: The 13 digit product code.
+  $x: The left edge of the barcode in the coordinate system of the transform.
+  $y: The top edge of the barcode in the coordinate system of the transform.
+  Use $set_styles to set the background to white and the color to black.
+  */
+  constructor .code_/string --x/int?=null --y/int?=null:
+    // The numbers go below the bar code in a way that depends on the size
+    // of the digits, so we need to take that into account when calculating
+    // the bounding box.
+    number_height_ = (sans10_.text_extent "8")[1]
+    height := EAN_13_HEIGHT + number_height_ - EAN_13_BOTTOM_SPACE
+    w := EAN_13_WIDTH
+    h := height + 1
+    super --x=x --y=y --w=w --h=h
+
+  l_ digit:
+    return EAN_13_L_CODES_[digit & 0xf]
+
+  g_ digit:
+    return EAN_13_G_CODES_[digit & 0xf]
+
+  r_ digit:
+    return (l_ digit) ^ 0x7f
+
+  // Make a white background behind the bar code and draw the digits along the bottom.
+  draw_background_ canvas/Canvas:
+    // Bar code coordinates.
+    text_x := EAN_13_QUIET_ZONE_WIDTH + EAN_13_START_WIDTH
+    text_y := EAN_13_HEIGHT + number_height_ - EAN_13_BOTTOM_SPACE + 1
+
+    canvas.text 1 text_y --text=code_[..1] --color=color_ --font=sans10_
+
+    code_[1..7].split "":
+      if it != "":
+        canvas.text text_x text_y --text=it --color=color_ --font=sans10_
+        text_x += EAN_13_DIGIT_WIDTH
+    text_x += EAN_13_MIDDLE_WIDTH - 1
+    code_[7..13].split "":
+      if it != "":
+        canvas.text text_x text_y --text=it --color=color_ --font=sans10_
+        text_x += EAN_13_DIGIT_WIDTH
+    marker_width := (sans10_.text_extent ">")[0]
+    text_x += EAN_13_START_WIDTH + EAN_13_QUIET_ZONE_WIDTH - marker_width
+    canvas.text text_x text_y --text=">" --color=color_ --font=sans10_
+
+  // Redraw routine.
+  custom_draw canvas/Canvas:
+    draw_background_ canvas
+
+    x := EAN_13_QUIET_ZONE_WIDTH
+    long_height := EAN_13_HEIGHT
+    short_height := EAN_13_HEIGHT - EAN_13_BOTTOM_SPACE
+    // Start bars: 101.
+    canvas.rectangle x     0 --w=1 --h=long_height --color=color_
+    canvas.rectangle x + 2 0 --w=1 --h=long_height --color=color_
+    x += 3
+    first_code := EAN_13_FIRST_CODES_[code_[0] & 0xf]
+    // Left digits using the L or G mapping.
+    for i := 1; i < 7; i++:
+      digit := code_[i]
+      code := ((first_code >> (6 - i)) & 1) == 0 ? (l_ digit) : (g_ digit)
+      for b := 6; b >= 0; b--:
+        if ((1 << b) & code) != 0:
+          canvas.rectangle x 0 --w=1 --h=short_height --color=color_
+        x++
+    // Middle bars: 01010
+    canvas.rectangle x + 1 0 --w=1 --h=long_height --color=color_
+    canvas.rectangle x + 3 0 --w=1 --h=long_height --color=color_
+    x += 5
+    // Left digits using the R mapping.
+    for i := 7; i < 13; i++:
+      digit := code_[i]
+      code := r_ digit
+      for b := 6; b >= 0; b--:
+        if ((1 << b) & code) != 0:
+          canvas.rectangle x 0 --w=1 --h=short_height --color=color_
+        x++
+    // End bars: 101.
+    canvas.rectangle x     0 --w=1 --h=long_height --color=color_
+    canvas.rectangle x + 2 0 --w=1 --h=long_height --color=color_

tests/barcode_visualized.toit

@@ -0,0 +1,37 @@
+// Copyright (C) 2023 Toitware ApS.
+// Use of this source code is governed by a Zero-Clause BSD license that can
+// be found in the TESTS_LICENSE file.
+
+// Tests drawing a supermarket-style bar code on a pixel display.
+
+import expect show *
+import pixel_display show *
+import pixel_display.bar_code show *
+import pixel_display.element show *
+import pixel_display.style show Style
+import .png_visualizer
+
+main args:
+  if args.size != 1:
+    print "Usage: script.toit png-basename"
+    exit 1
+  driver := SeveralColorPngVisualizer 120 160 args[0] --outline=SEVERAL_BLUE
+  display := SeveralColorPixelDisplay driver --portrait=false
+  display.background = SEVERAL_GRAY
+
+  style := Style --type_map={
+      "bar-code-ean": Style --color=SEVERAL_BLACK --background=SEVERAL_WHITE,
+  }
+
+  barcode := BarCodeEanElement --x=15 --y=15 "4035999001512"
+  display.add barcode
+  display.set_styles [style]
+  display.draw
+
+  barcode.move_to 20 20
+  display.draw
+
+  barcode.code = "4000417020000"
+  display.draw
+
+  driver.write_png