Implement text analyzer

Author: mrtcode

src/core/document.js

@@ -79,6 +79,7 @@ import { StreamsSequenceStream } from "./decode_stream.js";
 import { StructTreePage } from "./struct_tree.js";
 import { XFAFactory } from "./xfa/factory.js";
 import { XRef } from "./xref.js";
+import { Module } from "./module/module.js";
 
 const LETTER_SIZE_MEDIABOX = [0, 0, 612, 792];
 
@@ -1041,6 +1042,7 @@ class PDFDocument {
     this.pdfManager = pdfManager;
     this.stream = stream;
     this.xref = new XRef(stream, pdfManager);
+    this.module = new Module(this);
 
     const idCounters = {
       font: 0,

src/core/evaluator.js

@@ -2483,6 +2483,7 @@ class PartialEvaluator {
       transform: null,
       fontName: null,
       hasEOL: false,
+      chars: [],
     };
 
     // Use a circular buffer (length === 2) to save the last chars in the
@@ -2723,6 +2724,7 @@ class PartialEvaluator {
         transform: textChunk.transform,
         fontName: textChunk.fontName,
         hasEOL: textChunk.hasEOL,
+        chars: textChunk.chars,
       };
     }
 
@@ -3073,6 +3075,9 @@ class PartialEvaluator {
           scaledDim = 0;
         }
 
+        let prevWidth = textChunk.width;
+        let m = Util.transform(textState.ctm, textState.textMatrix);
+
         if (!font.vertical) {
           scaledDim *= textState.textHScale;
           intersector?.addGlyph(
@@ -3116,6 +3121,180 @@ class PartialEvaluator {
           textChunk.str.push(glyphUnicode);
         }
 
+        function closestStandardAngle(degrees) {
+          const standardAngles = [0, 90, 180, 270];
+          let closestAngle = standardAngles[0];
+          let minDifference = Math.abs(degrees - closestAngle);
+
+          for (let i = 1; i < standardAngles.length; i++) {
+            const difference = Math.abs(degrees - standardAngles[i]);
+            if (difference < minDifference) {
+              minDifference = difference;
+              closestAngle = standardAngles[i];
+            }
+          }
+
+          return closestAngle;
+        }
+
+        function matrixToDegrees(matrix) {
+          let radians = Math.atan2(matrix[1], matrix[0]);
+          if (radians < 0) {
+            radians += (2 * Math.PI);
+          }
+          let degrees = Math.round(radians * (180 / Math.PI));
+          degrees = degrees % 360;
+          if (degrees < 0) {
+            degrees += 360;
+          }
+          degrees = closestStandardAngle(degrees);
+          return degrees;
+        }
+
+        let rotation = matrixToDegrees(m);
+
+        let ascent = font.ascent;
+        let descent = font.descent;
+        if (descent > 0) {
+          descent = -descent;
+        }
+        if (ascent && descent) {
+          if (ascent > 1) {
+            ascent = 0.75;
+          }
+          if (descent < -0.5) {
+            descent = -0.25;
+          }
+        }
+        else {
+          ascent = 0.75;
+          descent = -0.25;
+        }
+
+        if (font.capHeight && font.capHeight < ascent && font.capHeight > 0) {
+          ascent = font.capHeight;
+        }
+
+        let charWidth = textChunk.width - prevWidth;
+        let rect = [0, textState.fontSize * descent, charWidth, textState.fontSize * ascent]
+
+        if (
+          font.isType3Font &&
+          textState.fontSize <= 1 &&
+          !isArrayEqual(textState.fontMatrix, FONT_IDENTITY_MATRIX)
+        ) {
+          const glyphHeight = font.bbox[3] - font.bbox[1];
+          if (glyphHeight > 0) {
+            rect[1] = font.bbox[1] * textState.fontMatrix[3];
+            rect[3] = font.bbox[3] * textState.fontMatrix[3];
+          }
+        }
+
+        let rect2 = [Infinity, Infinity, -Infinity, -Infinity];
+        Util.axialAlignedBoundingBox(rect, m, rect2);
+        rect = rect2;
+
+        let baselineRect = [Infinity, Infinity, -Infinity, -Infinity];
+        Util.axialAlignedBoundingBox([0, 0, 0, 0], m, baselineRect);
+        let baseline = 0;
+        if (rotation === 0 || rotation === 180) {
+          baseline = baselineRect[1];
+        }
+        else if (rotation === 90 || rotation === 270) {
+          baseline = baselineRect[0];
+        }
+
+        let p1 = [0, 0];
+        let p2 = [0, 1];
+
+        Util.applyTransform(p1, getCurrentTextTransform());
+        Util.applyTransform(p2, getCurrentTextTransform());
+
+        let [x1, y1] = p1;
+        let [x2, y2] = p2
+
+        let fontSize = Math.hypot(x1 - x2, y1 - y2);
+
+        let diagonal = rotation % 90 !== 0;
+
+        function normalizeChar(char) {
+          // Normalize the character to NFKD form to decompose ligatures and combined characters
+          let normalizedChar = char.normalize('NFKD');
+
+          // Handling known special cases where combining characters may still be decomposed
+          const specialCases = {
+            'e\u0301': 'é',  // e + ´ -> é
+            'a\u0301': 'á',  // a + ´ -> á
+            'i\u0301': 'í',  // i + ´ -> í
+            'o\u0301': 'ó',  // o + ´ -> ó
+            'u\u0301': 'ú',  // u + ´ -> ú
+            'e\u0300': 'è',  // e + ` -> è
+            'a\u0300': 'à',  // a + ` -> à
+            'i\u0300': 'ì',  // i + ` -> ì
+            'o\u0300': 'ò',  // o + ` -> ò
+            'u\u0300': 'ù',  // u + ` -> ù
+            'e\u0302': 'ê',  // e + ^ -> ê
+            'a\u0302': 'â',  // a + ^ -> â
+            'i\u0302': 'î',  // i + ^ -> î
+            'o\u0302': 'ô',  // o + ^ -> ô
+            'u\u0302': 'û',  // u + ^ -> û
+            'e\u0308': 'ë',  // e + ¨ -> ë
+            'a\u0308': 'ä',  // a + ¨ -> ä
+            'i\u0308': 'ï',  // i + ¨ -> ï
+            'o\u0308': 'ö',  // o + ¨ -> ö
+            'u\u0308': 'ü',  // u + ¨ -> ü
+            'c\u0327': 'ç',  // c + ¸ -> ç
+            'n\u0303': 'ñ',  // n + ˜ -> ñ
+            // Add other special cases here
+          };
+
+          // Check if the normalized character sequence matches a special case
+          if (specialCases[normalizedChar]) {
+            return specialCases[normalizedChar];
+          }
+
+          return normalizedChar;
+        }
+
+        let charCode = glyph.unicode.charCodeAt(0);
+
+        if (
+          glyph.unicode !== ' ' &&
+          fontSize !== 0 &&
+          // Skip null and other control characters to avoid breaking strings, DOM, end even browsers…
+          // TODO: Consider skipping other non-printable characters as well
+          // TODO: Determine whether it's better to skip or replace these characters
+          //  since we may need to keep PDF.js text layer character offsets aligned with
+          //  Zotero reader text layer character offsets
+          !(
+            // ASCII control characters
+            (charCode >= 0x00 && charCode <= 0x1F) ||
+            // Extended control characters
+            (charCode >= 0x7F && charCode <= 0x9F)
+          )
+        ) {
+          textChunk.chars.push({
+            // Decomposed ligatures, normalized Arabic characters
+            c: normalizeChar(glyphUnicode),
+            // Normalizes Arabic characters others characters where length remains 1, but preserves
+            // ligatures and more importantly avoids 'e\u00be' being converted into 'e \u0301'
+            // which is quite common in Spanish author names and because of the space prevents
+            // author name recognition
+            // NOTE: THIS CAN STILL HAVE DECOMPOSED LIGATURES IF THE FONT HAS ITS OWN CHARACTER MAPPING,
+            // THEREFORE CONSIDER DITCHING THIS PROPERTY
+            u: glyphUnicode.length === 1 ? glyphUnicode : glyph.unicode,
+            rect,
+            fontSize,
+            fontName: textState.font.name,
+            bold: textState.font.bold,
+            italic: textState.font.italic,
+            glyphWidth,
+            baseline,
+            rotation,
+            diagonal,
+          });
+        }
+
         if (charSpacing) {
           if (!font.vertical) {
             textState.translateTextMatrix(
@@ -3198,6 +3377,7 @@ class PartialEvaluator {
       textContent.items.push(runBidiTransform(textContentItem));
       textContentItem.initialized = false;
       textContentItem.str.length = 0;
+      textContentItem.chars = [];
     }
 
     function enqueueChunk(batch = false) {