[WIP] Adjust the view using native content transform

paper2remarkable/adjust.py

@@ -0,0 +1,107 @@
+# -*- coding: utf-8 -*-
+
+"""Code for adjusting view
+
+Author: G.J.J. van den Burg
+License: See LICENSE file
+Copyright: 2021, G.J.J. van den Burg
+
+"""
+
+from collections import namedtuple
+
+from .crop import Cropper
+
+# This is an experimental module that aims to use the reMarkable's own file
+# format to adjust the view of a PDF, instead of setting the bounding box as is
+# done in the "Cropper". At the moment this is work in progress.
+#
+# To the best of my knowledge the content file format of the reMarkable is not
+# extensively documented outside what is available
+# [here](https://remarkablewiki.com/tech/filesystem#content_file_format). This
+# module will mainly rely on the "transform" attribute, which is largely
+# undocumented.
+#
+# TODO:
+#  - Figure out what m31 and m32 do in the "transform".
+#  - Test if we can reliably do left/center/right crops using transforms.
+#  - Add a UI flag to use adjust instead of crop (as well as config option)
+#  - Figure out how to deliver a ZIP instead of a PDF using rmapi/rmapy
+
+
+class Transform:
+    def __init__(self, transform=None):
+        self.transform = transform or self._default_transform()
+
+    def _default_transform(self):
+        keys = ["m%i%i" % (i, j) for i in range(3) for j in range(3)]
+        keys.sort()
+        transform = {k: 0 for k in keys}
+        transform["m11"] = transform["m22"] = transform["m33"] = 1
+        return transform
+
+
+# (0, 0) bottom left: so xmin = left margin, xmax is margin + content
+BBox = namedtuple("BBox", ["xmin", "xmax", "ymin", "ymax"])
+
+PageDims = namedtuple("PageDims", ["width", "height"])
+
+
+class Adjuster:
+    def __init__(self, input_file, pdftoppm_path="pdftoppm"):
+        self.cropper = Cropper(
+            input_file=input_file, pdftoppm_path=pdftoppm_path
+        )
+
+    def left(self, margins=1) -> Transform:
+        return self.process_file(kind="left", margins=margins)
+
+    def center(self, padding=15) -> Transform:
+        return self.process_file(kind="center", padding=padding)
+
+    def right(self, padding=15) -> Transform:
+        return self.process_file(kind="right", padding=padding)
+
+    def process_file(self, kind="left", **kwargs):
+        outerbbox = BBox(
+            xmin=float("inf"),
+            xmax=-float("inf"),
+            ymin=float("inf"),
+            ymax=-float("inf"),
+        )
+        outerpage = PageDims(-float("inf"), -float("inf"))
+
+        for page_idx in range(self.cropper.reader.getNumPages()):
+            tmpfname = self.cropper.export_page(page_idx)
+            raw_bbox = self.cropper.get_raw_bbox(tmpfname)
+            page_dims = PageDims(width=raw_bbox[4], height=raw_bbox[5])
+
+            if kind == "left":
+                bbox = self.cropper.get_bbox(tmpfname, **kwargs)
+            elif kind == "center":
+                bbox = self.cropper.get_center_bbox(tmpfname, **kwargs)
+            elif kind == "right":
+                bbox = self.cropper.get_right_bbox(tmpfname, **kwargs)
+            else:
+                raise ValueError(f"Unknown crop type: {kind}")
+
+            page_bbox = BBox(
+                xmin=bbox[0], xmax=bbox[2], ymin=bbox[1], ymax=bbox[3]
+            )
+
+            outerbbox.xmin = min(outerbbox.xmin, page_bbox.xmin)
+            outerbbox.ymin = min(outerbbox.ymin, page_bbox.ymin)
+            outerbbox.xmax = max(outerbbox.xmax, page_bbox.xmax)
+            outerbbox.ymax = max(outerbbox.ymax, page_bbox.ymax)
+
+            outerpage.width = max(outerpage.width, page_dims.width)
+            outerpage.height = max(outerpage.height, page_dims.height)
+
+        bbox_width = outerbbox.xmax - outerbbox.xmin
+        bbox_height = outerbbox.ymax - outerbbox.ymin
+
+        transform = Transform()
+        transform["m11"] = outerpage.height / bbox_height
+        transform["m22"] = outerpage.width / bbox_width
+        # TODO Figure out what m31 and m32 do, they're likely offsets
+        return transform