Add "svg-compressed" to create a simple classic QR Code with compressed file size.

qrcode/console_scripts.py

@@ -28,6 +28,7 @@
     "svg": "qrcode.image.svg.SvgImage",
     "svg-fragment": "qrcode.image.svg.SvgFragmentImage",
     "svg-path": "qrcode.image.svg.SvgPathImage",
+    "svg-compressed": "qrcode.image.svg.SvgCompressedImage",
     # Keeping for backwards compatibility:
     "pymaging": "qrcode.image.pure.PymagingImage",
 }

qrcode/image/styles/moduledrawers/svg.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import abc
 from decimal import Decimal
 from typing import TYPE_CHECKING, NamedTuple
@@ -21,7 +23,7 @@ class Coords(NamedTuple):
 
 
 class BaseSvgQRModuleDrawer(QRModuleDrawer):
-    img: "SvgFragmentImage"
+    img: SvgFragmentImage
 
     def __init__(self, *, size_ratio: Decimal = Decimal(1), **kwargs):
         self.size_ratio = size_ratio
@@ -97,7 +99,7 @@ def el(self, box):
 
 
 class SvgPathQRModuleDrawer(BaseSvgQRModuleDrawer):
-    img: "SvgPathImage"
+    img: SvgPathImage
 
     def drawrect(self, box, is_active: bool):
         if not is_active:
@@ -108,6 +110,20 @@ def drawrect(self, box, is_active: bool):
     def subpath(self, box) -> str: ...
 
 
+class SvgCompressedDrawer(BaseSvgQRModuleDrawer):
+    img: SvgPathImage
+
+    def drawrect(self, box, is_active: bool):
+        if not is_active:
+            return
+        coords = self.coords(box)
+        x0 = self.img.units(coords.x0, text=False)
+        y0 = self.img.units(coords.y0, text=False)
+        assert self.img.units(coords.x1, text=False) - 1 == x0
+        assert self.img.units(coords.y1, text=False) - 1 == y0
+        self.img._points.append([int(x0), int(y0)])
+
+
 class SvgPathSquareDrawer(SvgPathQRModuleDrawer):
     def subpath(self, box) -> str:
         coords = self.coords(box)

qrcode/image/svg.py

@@ -1,4 +1,5 @@
 import decimal
+import enum
 from decimal import Decimal
 from typing import Optional, Union, overload, Literal
 
@@ -164,6 +165,267 @@ def process(self):
         self._img.append(self.path)
 
 
+class SvgCompressedImage(SvgImage):
+    """
+    SVG image builder with goal of the smallest possible output, at least among
+    algorithms with predictable fast run time.
+    """
+
+    QR_PATH_STYLE = {
+        "fill": "#000000",
+        "fill-opacity": "1",
+        "fill-rule": "nonzero",
+        "stroke": "none",
+    }
+
+    needs_processing = True
+    path: Optional[ET.Element] = None
+    default_drawer_class: type[QRModuleDrawer] = svg_drawers.SvgCompressedDrawer
+
+    def __init__(self, *args, **kwargs):
+        self._points = []
+        super().__init__(*args, **kwargs)
+
+    def _svg(self, viewBox=None, **kwargs):
+        if viewBox is None:
+            dimension = self.units(self.pixel_size, text=False)
+            # Save characters by moving real pixels to start at 0,0 with a negative
+            # offset for the border, with more real pixels having lower digit counts.
+            viewBox = "-{b} -{b} {d} {d}".format(d=dimension, b=self.border)
+        return super()._svg(viewBox=viewBox, **kwargs)
+
+    def _generate_subpaths(self):
+        """
+        Yield a series of paths which walk the grid, drawing squares on,
+        and also drawing reverse transparency holes, to complete the SVG.
+        """
+        # what we should make, juxtaposed against what we currently have
+        goal = [[0] * (self.width + 2) for i in range(self.width + 2)]
+        curr = [[0] * (self.width + 2) for i in range(self.width + 2)]
+        for point in self._points:
+            # The +1 -1 allows the path walk logic to not worry about image edges.
+            goal[point[0] - self.border + 1][point[1] - self.border + 1] = 1
+
+        def abs_or_delta(cmds, curr_1, last_1, curr_2=None, last_2=None):
+            """Use whichever is shorter: the absolute command, or delta command."""
+
+            def opt_join(a, b):
+                if b is None:
+                    return "%d" % a
+                return "%d" % a + ("" if b < 0 else " ") + "%d" % b
+
+            return min(
+                [
+                    cmds[0]
+                    + opt_join(
+                        curr_1 - last_1, curr_2 - last_2 if curr_2 is not None else None
+                    ),
+                    # The +1 -1 allows the path walk logic to not worry about image edges.
+                    cmds[1]
+                    + opt_join(curr_1 - 1, curr_2 - 1 if curr_2 is not None else None),
+                ],
+                key=len,
+            )
+
+        class WD(enum.IntEnum):
+            North = 1
+            South = 2
+            East = 3
+            West = 4
+
+        class PathChain:
+            __slots__ = ["cmds", "next"]
+
+            def __init__(self):
+                self.cmds = ""
+                self.next = None
+
+            def create_next(self):
+                self.next = PathChain()
+                return self.next
+
+        # Old cursor position allows optimizing with "m" sometimes instead of "M".
+        # The +1 -1 allows the path walk logic to not worry about image edges.
+        old_cursor = (1, 1)
+        fullpath_head = fullpath_tail = None
+        fullpath_splice_points = {}
+
+        # Go over the grid, creating the paths. This ordering seems to work fairly
+        # well, although it's not necessarily optimal. Unfortunately optimal is a
+        # traveling salesman problem, and it's not obvious whether there's any
+        # significantly better possible ordering in general.
+        for search_y in range(self.width + 2):
+            for search_x in range(self.width + 2):
+                if goal[search_x][search_y] == curr[search_x][search_y]:
+                    continue
+
+                # Note, the 'm' here is starting from the old cursor spot, which (as per SVG
+                # spec) is not the close path spot. We could test for both, trying a 'z' to
+                # to save characters for the next 'm'. However, the mathematically first
+                # opportunity would be a convert of 'm1 100' to 'm1 9', so would require a
+                # straight line of 91 pairs of identical pixels. I believe the QR spec allows
+                # for that, but it is essentially impossible by chance.
+                (start_x, start_y) = (search_x, search_y)
+                subpath_head = subpath_tail = PathChain()
+                subpath_head.cmds = abs_or_delta(
+                    "mM", start_x, old_cursor[0], start_y, old_cursor[1]
+                )
+                path_flips = {}
+                do_splice = (
+                    False  # The point where we are doing a splice, to save on 'M's.
+                )
+                subpath_splice_points = {}
+                paint_on = goal[start_x][start_y]
+                path_dir = WD.East if paint_on else WD.South
+                (curr_x, curr_y) = (last_x, last_y) = (start_x, start_y)
+
+                def should_switch_to_splicing():
+                    nonlocal do_splice, start_x, start_y, subpath_head, subpath_tail
+                    if not do_splice and (curr_x, curr_y) in fullpath_splice_points:
+                        subpath_head = subpath_tail = PathChain()
+                        path_flips.clear()
+                        subpath_splice_points.clear()
+                        do_splice |= True
+                        (start_x, start_y) = (curr_x, curr_y)
+                        return True
+                    return False
+
+                def add_to_splice_points():
+                    nonlocal subpath_tail
+                    if (curr_x, curr_y) in subpath_splice_points:
+                        # we hit a splice point a second time, so topology dictates it's done
+                        subpath_splice_points.pop((curr_x, curr_y))
+                    else:
+                        subpath_splice_points[curr_x, curr_y] = subpath_tail
+                        subpath_tail = subpath_tail.create_next()
+
+                # Immediately check for a need to splice in, right from the starting point.
+                should_switch_to_splicing()
+
+                while True:
+                    if path_dir == WD.East:
+                        while goal[curr_x][curr_y] and not goal[curr_x][curr_y - 1]:
+                            if curr_x not in path_flips:
+                                path_flips[curr_x] = []
+                            path_flips[curr_x].append(curr_y)
+                            curr_x += 1
+                        assert curr_x != last_x
+                        path_dir = WD.North if goal[curr_x][curr_y - 1] else WD.South
+                        if do_splice or (curr_x, curr_y) != (start_x, start_y):
+                            subpath_tail.cmds += abs_or_delta("hH", curr_x, last_x)
+
+                        # only a left turn with a hole coming up on the right is spliceable
+                        if path_dir == WD.North and not goal[curr_x][curr_y]:
+                            add_to_splice_points()
+
+                        if (curr_x, curr_y) == (start_x, start_y):
+                            break  # subpath is done
+                        if should_switch_to_splicing():
+                            continue
+                    elif path_dir == WD.West:
+                        while (
+                            not goal[curr_x - 1][curr_y]
+                            and goal[curr_x - 1][curr_y - 1]
+                        ):
+                            curr_x -= 1
+                            if curr_x not in path_flips:
+                                path_flips[curr_x] = []
+                            path_flips[curr_x].append(curr_y)
+                        assert curr_x != last_x
+                        path_dir = WD.South if goal[curr_x - 1][curr_y] else WD.North
+                        if do_splice or (curr_x, curr_y) != (start_x, start_y):
+                            subpath_tail.cmds += abs_or_delta("hH", curr_x, last_x)
+
+                        # only a left turn with a hole coming up on the right is spliceable
+                        if path_dir == WD.South and not goal[curr_x - 1][curr_y - 1]:
+                            add_to_splice_points()
+
+                        if (curr_x, curr_y) == (start_x, start_y):
+                            break  # subpath is done
+                        if should_switch_to_splicing():
+                            continue
+                    elif path_dir == WD.North:
+                        while (
+                            goal[curr_x][curr_y - 1]
+                            and not goal[curr_x - 1][curr_y - 1]
+                        ):
+                            curr_y -= 1
+                        assert curr_y != last_y
+                        path_dir = WD.West if goal[curr_x - 1][curr_y - 1] else WD.East
+                        if do_splice or (curr_x, curr_y) != (start_x, start_y):
+                            subpath_tail.cmds += abs_or_delta("vV", curr_y, last_y)
+
+                        # only a left turn with a hole coming up on the right is spliceable
+                        if path_dir == WD.West and not goal[curr_x][curr_y - 1]:
+                            add_to_splice_points()
+
+                        if (curr_x, curr_y) == (start_x, start_y):
+                            break  # subpath is done
+                        if should_switch_to_splicing():
+                            continue
+                    elif path_dir == WD.South:
+                        while not goal[curr_x][curr_y] and goal[curr_x - 1][curr_y]:
+                            curr_y += 1
+                        assert curr_y != last_y
+                        path_dir = WD.East if goal[curr_x][curr_y] else WD.West
+                        if do_splice or (curr_x, curr_y) != (start_x, start_y):
+                            subpath_tail.cmds += abs_or_delta("vV", curr_y, last_y)
+
+                        # only a left turn with a hole coming up on the right is spliceable
+                        if path_dir == WD.East and not goal[curr_x - 1][curr_y]:
+                            add_to_splice_points()
+
+                        if (curr_x, curr_y) == (start_x, start_y):
+                            break  # subpath is done
+                        if should_switch_to_splicing():
+                            continue
+                    else:
+                        raise
+                    assert (last_x, last_y) != (curr_x, curr_y), goal
+                    (last_x, last_y) = (curr_x, curr_y)
+
+                if do_splice:
+                    subpath_tail.next = fullpath_splice_points[start_x, start_y].next
+                    fullpath_splice_points[start_x, start_y].next = subpath_head
+                else:
+                    if not fullpath_head:
+                        fullpath_head = subpath_head
+                    else:
+                        fullpath_tail.next = subpath_head
+                    fullpath_tail = subpath_tail
+                    old_cursor = (last_x, last_y)
+
+                for k, v in subpath_splice_points.items():
+                    if k in fullpath_splice_points:
+                        # we hit a splice point a second time, so topology dictates it's done
+                        fullpath_splice_points.pop(k)
+                    else:
+                        # merge new splice point
+                        fullpath_splice_points[k] = v
+
+                # Note that only one dimension (which was arbitrary chosen here as
+                # horizontal) needs to be evaluated to determine all of the pixel flips.
+                for x, ys in path_flips.items():
+                    ys = sorted(ys, reverse=True)
+                    while len(ys) > 1:
+                        for y in range(ys.pop(), ys.pop()):
+                            curr[x][y] = paint_on
+        assert fullpath_splice_points == {}, fullpath_splice_points
+        while fullpath_head:
+            yield fullpath_head.cmds
+            fullpath_head = fullpath_head.next
+
+    def process(self):
+        # Store the path just in case someone wants to use it again or in some
+        # unique way.
+        self.path = ET.Element(
+            ET.QName("path"),  # type: ignore
+            d="".join(self._generate_subpaths()),
+            **self.QR_PATH_STYLE,
+        )
+        self._img.append(self.path)
+
+
 class SvgFillImage(SvgImage):
     """
     An SvgImage that fills the background to white.

qrcode/tests/test_qrcode_svg.py

@@ -23,6 +23,13 @@ def test_render_svg_path():
     img.save(io.BytesIO())
 
 
+def test_render_svg_compressed():
+    qr = qrcode.QRCode()
+    qr.add_data(UNICODE_TEXT)
+    img = qr.make_image(image_factory=svg.SvgCompressedImage)
+    img.save(io.BytesIO())
+
+
 def test_render_svg_fragment():
     qr = qrcode.QRCode()
     qr.add_data(UNICODE_TEXT)