Created
March 22, 2023 19:51
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Extra the letters of a PDF document and their positions
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| /* | |
| When loading the PDF document, you need to set the `fontExtraProperties` parameter to `true`. e.g. | |
| getDocument({ | |
| ..., | |
| fontExtraProperties: true | |
| }) | |
| */ | |
| var generateId = () => { | |
| return ( | |
| Date.now().toString(36) + | |
| Math.floor( | |
| Math.pow(10, 12) + Math.random() * 9 * Math.pow(10, 12) | |
| ).toString(36) | |
| ) | |
| } | |
| function itemToRect(item, viewport, heightScale=1) { | |
| const transformed = Util.transform( | |
| viewport.transform, | |
| item.transform | |
| ) | |
| let [left, top] = Util.applyTransform( | |
| [0, 1], | |
| transformed | |
| ) | |
| let width = Util.applyTransform( | |
| [item.width, 0], | |
| viewport.transform | |
| )[0] | |
| let height = Util.applyTransform( | |
| [item.height, 0], | |
| viewport.transform | |
| )[0] | |
| left /= viewport.width | |
| width /= viewport.width | |
| top /= viewport.height | |
| height /= viewport.height | |
| height *= heightScale | |
| return { left, top, width, height } | |
| } | |
| function* itemToRects(item, page, heightScale) { | |
| const { viewport } = viewer.getPageView(page.pageNumber - 1) | |
| const bbox = { | |
| ...itemToRect(item, viewport, heightScale), | |
| page: page.pageNumber | |
| } | |
| const itemFont = page.commonObjs.get(item.fontName) | |
| const letterItems = [] | |
| let itemFontWidth = 0 | |
| let itemText = item.str | |
| if (item.hasEOL) { | |
| itemText += '\n' | |
| } | |
| for (const letter of itemText) { | |
| const fontWidth = itemFont.widths[ | |
| letter.charCodeAt() | |
| ] || 0 | |
| letterItems.push({ | |
| letter, | |
| fontWidth, | |
| leftOffset: itemFontWidth | |
| }) | |
| itemFontWidth += fontWidth | |
| } | |
| for (const letterItem of letterItems) { | |
| const { letter, fontWidth, leftOffset } = letterItem | |
| let left = 0 | |
| let width = 0 | |
| if (itemFontWidth > 0) { | |
| left = leftOffset / itemFontWidth * bbox.width + bbox.left | |
| width = fontWidth / itemFontWidth * bbox.width | |
| } | |
| yield { | |
| letter, | |
| left, | |
| width, | |
| page: bbox.page, | |
| top: bbox.top, | |
| height: bbox.height, | |
| } | |
| } | |
| } | |
| async function getLetterRects(page) { | |
| const { items } = await page.getTextContent() | |
| const formattedLetterRects = [] | |
| for (const item of items) { | |
| const letterRects = itemToRects(item, page, heightScale=1.25) | |
| for (const letterRect of letterRects) { | |
| const { letter, ...rect } = letterRect | |
| formattedLetterRects.push({ | |
| id: generateId(), | |
| text: letter, | |
| position: { | |
| page: page.pageNumber, | |
| rects: [rect] | |
| } | |
| }) | |
| } | |
| } | |
| return formattedLetterRects | |
| } |
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