Detect footnotes transformation

* transform height with fontHeight

src/javascript/components/LoadingView.jsx

@@ -53,14 +53,21 @@ export default class LoadingView extends React.Component {
             anounceInitialParseFunction(pdfPages);
             for (var j = 1; j <= numPages; j++) {
                 pdfDocument.getPage(j).then(function(page) {
+                    var scale = 1.0;
+                    var viewport = page.getViewport(scale);
                     page.getTextContent().then(function(textContent) {
-                        // console.debug(textContent);
                         const textItems = textContent.items.map(function(item) {
+                            var tx = PDFJS.Util.transform( // eslint-disable-line no-undef
+                                viewport.transform,
+                                item.transform
+                            );
+                            var fontHeight = Math.sqrt((tx[2] * tx[2]) + (tx[3] * tx[3]));
+
                             return new TextItem({
                                 x: item.transform[4],
                                 y: item.transform[5],
                                 width: item.width,
-                                height: item.height,
+                                height: item.height / fontHeight,
                                 text: item.str
                             });
                         });

src/javascript/functions.jsx

@@ -0,0 +1,13 @@
+export function isDigit(charCode) {
+    return charCode >= 48 && charCode <= 57;
+}
+
+export function isNumber(string) {
+    for (var i = 0; i < string.length; i++) {
+        const charCode = string.charCodeAt(i);
+        if (!isDigit(charCode)) {
+            return false;
+        }
+    }
+    return true;
+}

src/javascript/models/AppState.jsx

@@ -3,6 +3,7 @@ import { Enum } from 'enumify';
 import NoOp from './transformations/NoOp.jsx';
 import RoundCoordinates from './transformations/RoundCoordinates.jsx';
 import CombineSameY from './transformations/CombineSameY.jsx';
+import DetectFootnotes from './transformations/DetectFootnotes.jsx'
 import RemoveRepetitiveElements from './transformations/RemoveRepetitiveElements.jsx'
 import ToTextPages from './transformations/ToTextPages.jsx';
 import ToSingleTextPage from './transformations/ToSingleTextPage.jsx'
@@ -19,6 +20,7 @@ export default class AppState {
             new NoOp,
             new RoundCoordinates(),
             new CombineSameY(),
+            new DetectFootnotes(),
             new RemoveRepetitiveElements(),
             new ToTextPages(),
             new ToSingleTextPage()];

src/javascript/models/transformations/DetectFootnotes.jsx

@@ -0,0 +1,75 @@
+import Transformation from './Transformation.jsx';
+import TextItem from '../TextItem.jsx';
+import PdfPage from '../PdfPage.jsx';
+import ContentView from '../ContentView.jsx';
+import Annotation from '../Annotation.jsx';
+
+import { isNumber } from '../../functions.jsx'
+
+export default class DetectFootnotes extends Transformation {
+
+    constructor() {
+        super("Detect Footnotes");
+    }
+
+    contentView() {
+        return ContentView.PDF;
+    }
+
+    transform(pages:PdfPage[]) {
+
+        var nextFooterNumber = 1;
+        var potentialFootnoteItem;
+
+        const removedAnnotation = new Annotation({
+            category: 'removed',
+            color: 'red'
+        });
+
+        return pages.map(page => {
+            const newTextItems = [];
+            for (var i = 0; i < page.textItems.length; i++) {
+                const item = page.textItems[i];
+                if (potentialFootnoteItem) {
+                    if (potentialFootnoteItem.y - item.y < item.height) {
+                        potentialFootnoteItem.annotation = removedAnnotation;
+                        item.annotation = removedAnnotation;
+                        newTextItems.push(potentialFootnoteItem);
+                        newTextItems.push(item);
+                        newTextItems.push(new TextItem({
+                            x: potentialFootnoteItem.x,
+                            y: item.y,
+                            width: potentialFootnoteItem.width + item.width,
+                            height: item.height,
+                            text: '[' + potentialFootnoteItem.text + '] ' + item.text,
+                            annotation: new Annotation({
+                                category: 'footnote',
+                                color: 'green'
+                            })
+                        }));
+                        //TODO repsect multiline!!
+                        nextFooterNumber++;
+                    }
+                    potentialFootnoteItem = null;
+                } else if (isNumber(item.text) && parseInt(item.text) == nextFooterNumber && i > 0 && i < page.textItems.length - 1 && page.textItems[i - 1].y !== page.textItems[i + 1].y) {
+                    potentialFootnoteItem = item;
+                } else {
+                    newTextItems.push(item);
+                }
+            }
+            return {
+                ...page,
+                textItems: newTextItems
+            };
+        });
+    }
+
+    processAnnotations(pages:PdfPage[]) {
+        pages.forEach(page => {
+            page.textItems = page.textItems.filter(textItem => !textItem.annotation || textItem.annotation.category !== 'removed');
+            page.textItems.forEach(textItem => textItem.annotation = null)
+        });
+        return pages;
+    }
+
+}

src/javascript/models/transformations/RemoveRepetitiveElements.jsx

@@ -3,14 +3,15 @@ import PdfPage from '../PdfPage.jsx';
 import ContentView from '../ContentView.jsx';
 import Annotation from '../Annotation.jsx';
 
+import { isDigit } from '../../functions.jsx'
+
 
 function hashCodeIgnoringNumbers(string) {
-    var hash = 0, i, charCode, len, isNumber;
+    var hash = 0, i, charCode, len;
     if (string.length === 0) return hash;
     for (i = 0, len = string.length; i < len; i++) {
         charCode = string.charCodeAt(i);
-        isNumber = charCode >= 48 && charCode <= 57;
-        if (!isNumber) {
+        if (!isDigit(charCode)) {
             hash = ((hash << 5) - hash) + charCode;
             hash |= 0; // Convert to 32bit integer
         }