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Add clustering based on bounding box to fix interweaving text in multicolumn layouts, fixes #457 #484

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Add clustering based on bounding box to fix interweaving text in multicolumn layouts, fixes #457 #484

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69 changes: 40 additions & 29 deletions src/Extraction/Text/TextExtractor.php
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
use PrinsFrank\PdfParser\Document\ContentStream\PositionedText\PositionedTextElement;
use PrinsFrank\PdfParser\Document\Object\Decorator\Page;
use PrinsFrank\PdfParser\Exception\PdfParserException;
use PrinsFrank\PdfParser\Extraction\Text\TextGrouping\Clustering\BoundingBoxClusterer;
use PrinsFrank\PdfParser\Extraction\Text\TextGrouping\LineGrouping\TextOverlapStrategy;

class TextExtractor {
Expand All @@ -13,43 +14,53 @@ class TextExtractor {
* @throws PdfParserException
*/
public static function extractText(array $positionedTextElements, Page $page): string {
$lineGroupedElements = TextOverlapStrategy::group($positionedTextElements);

$text = '';
foreach ($lineGroupedElements as $i => $positionedTextElementsForLine) {
$previousTextElementOnLine = null;
$clusters = BoundingBoxClusterer::cluster($positionedTextElements, $page);
foreach ($clusters as $i => $cluster) {
if ($i !== 0) {
$text .= "\n";
$previousCluster = $clusters[$i - 1];
if (min($previousCluster->top, $cluster->top) <= max($previousCluster->bottom, $cluster->bottom)) {
$text .= "\n";
$previousTextElementOnLine = null;
}
}

$previousTextElementOnLine = null;
foreach ($positionedTextElementsForLine as $positionedTextElement) {
$elementText = $positionedTextElement->getText($page);
if ($elementText === '') {
$previousTextElementOnLine = $positionedTextElement;
continue;
foreach (TextOverlapStrategy::group($cluster->elements) as $j => $positionedTextElementsForLine) {
if ($j !== 0) {
$text .= "\n";
$previousTextElementOnLine = null;
}

if ($previousTextElementOnLine !== null) {
$gap = $positionedTextElement->absoluteMatrix->offsetX
- $previousTextElementOnLine->absoluteMatrix->offsetX
- $previousTextElementOnLine->getAdvanceWidth($page);

$wordBreakThreshold = $previousTextElementOnLine->textState->getFontSize()
* $previousTextElementOnLine->absoluteMatrix->scaleX
* ($previousTextElementOnLine->textState->scale / 100)
* PositionedTextElement::WORD_BREAK_THRESHOLD_EM;

if (
$gap >= $wordBreakThreshold
&& str_ends_with($text, ' ') === false
&& str_starts_with($elementText, ' ') === false
) {
$text .= ' ';
foreach ($positionedTextElementsForLine as $positionedTextElement) {
$elementText = $positionedTextElement->getText($page);
if ($elementText === '') {
$previousTextElementOnLine = $positionedTextElement;
continue;
}
}

$text .= $elementText;
$previousTextElementOnLine = $positionedTextElement;
if ($previousTextElementOnLine !== null) {
$gap = $positionedTextElement->absoluteMatrix->offsetX
- $previousTextElementOnLine->absoluteMatrix->offsetX
- $previousTextElementOnLine->getAdvanceWidth($page);

$wordBreakThreshold = $previousTextElementOnLine->textState->getFontSize()
* $previousTextElementOnLine->absoluteMatrix->scaleX
* ($previousTextElementOnLine->textState->scale / 100)
* PositionedTextElement::WORD_BREAK_THRESHOLD_EM;

if (
$gap >= $wordBreakThreshold
&& str_ends_with($text, ' ') === false
&& str_starts_with($elementText, ' ') === false
) {
$text .= ' ';
}
}

$text .= $elementText;
$previousTextElementOnLine = $positionedTextElement;
}
}
}

Expand Down
84 changes: 84 additions & 0 deletions src/Extraction/Text/TextGrouping/Clustering/BoundingBoxClusterer.php
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Original file line number Diff line number Diff line change
@@ -0,0 +1,84 @@
<?php declare(strict_types=1);

namespace PrinsFrank\PdfParser\Extraction\Text\TextGrouping\Clustering;

use PrinsFrank\PdfParser\Document\ContentStream\PositionedText\PositionedTextElement;
use PrinsFrank\PdfParser\Document\Object\Decorator\Page;

class BoundingBoxClusterer {
/**
* @param list<PositionedTextElement> $positionedTextElements
* @return list<Cluster>
*/
public static function cluster(array $positionedTextElements, Page $page): array {
usort(
$positionedTextElements,
fn(PositionedTextElement $a, PositionedTextElement $b): int => $b->absoluteMatrix->offsetY <=> $a->absoluteMatrix->offsetY,
);

$processedIndices = $clusters = [];
$nrOfItems = count($positionedTextElements);
for ($i = 0; $i < $nrOfItems; $i++) {
if (isset($processedIndices[$i])) {
continue;
}

$firstClusterElement = $positionedTextElements[$i];
$cluster = [$firstClusterElement];
$processedIndices[$i] = true;

$clusterLeft = $firstClusterElement->absoluteMatrix->offsetX;
$clusterRight = $clusterLeft + $firstClusterElement->getAdvanceWidth($page);
$clusterBottom = $firstClusterElement->absoluteMatrix->offsetY;
$clusterTop = $clusterBottom + $firstClusterElement->getHeight();

$previousPassResultedInNewElements = true;
while ($previousPassResultedInNewElements) {
$previousPassResultedInNewElements = false;

for ($j = $i + 1; $j < $nrOfItems; $j++) {
if (isset($processedIndices[$j])) {
continue;
}

$candidate = $positionedTextElements[$j];
$candidateRight = $candidate->absoluteMatrix->offsetX + $candidate->getAdvanceWidth($page);
$candidateTop = $candidate->absoluteMatrix->offsetY + $candidate->getHeight();
if (max(0, $clusterLeft - $candidateRight, $candidate->absoluteMatrix->offsetX - $clusterRight) <= 5
&& max(0, $clusterBottom - $candidateTop, $candidate->absoluteMatrix->offsetY - $clusterTop) <= 7) {
$cluster[] = $candidate;
$processedIndices[$j] = true;
$previousPassResultedInNewElements = true;

$clusterLeft = min($clusterLeft, $candidate->absoluteMatrix->offsetX);
$clusterRight = max($clusterRight, $candidateRight);
$clusterBottom = min($clusterBottom, $candidate->absoluteMatrix->offsetY);
$clusterTop = max($clusterTop, $candidateTop);
}
}
}

$clusters[] = new Cluster($cluster, $clusterLeft, $clusterRight, $clusterBottom, $clusterTop);
}

usort(
$clusters,
function (Cluster $a, Cluster $b): int {
$aHeight = $a->top - $a->bottom;
$bHeight = $b->top - $b->bottom;
$smallestHeight = min($aHeight, $bHeight);
if ($smallestHeight > 0) {
$overlap = min($a->top, $b->top) - max($a->bottom, $b->bottom);
$overlapPercentage = ($overlap / $smallestHeight) * 100;
if ($overlapPercentage >= 90) {
return $a->left <=> $b->left;
}
}

return $b->top <=> $a->top;
},
);

return $clusters;
}
}
16 changes: 16 additions & 0 deletions src/Extraction/Text/TextGrouping/Clustering/Cluster.php
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Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
<?php declare(strict_types=1);

namespace PrinsFrank\PdfParser\Extraction\Text\TextGrouping\Clustering;

use PrinsFrank\PdfParser\Document\ContentStream\PositionedText\PositionedTextElement;

readonly class Cluster {
/** @param list<PositionedTextElement> $elements */
public function __construct(
public array $elements,
public float $left,
public float $right,
public float $bottom,
public float $top,
) { }
}
1 change: 0 additions & 1 deletion src/Extraction/Text/TextGrouping/LineGrouping/TextOverlapStrategy.php
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,6 @@ public static function group(array $positionedTextElements): iterable {
continue;
}

/** @var PositionedTextElement $highestPositionedTextElement */
$highestPositionedTextElement = $positionedTextElements[$i];
$highestPositionedTextElementBottom = $highestPositionedTextElement->absoluteMatrix->offsetY;
$highestPositionedTextElementHeight = $highestPositionedTextElement->getHeight();
Expand Down
46 changes: 30 additions & 16 deletions tests/Samples/files/gdocs-lorem-ipsum-with-titles-and-formatting/contents.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -79,11 +79,15 @@ pages:
● Ut autem excepturi ut sequi laboriosam est quas debitis et placeat consequatur!
-
text: |-
●
●
●
●
● Qui autem voluptas eum deserunt dolor.
● In nesciunt quia qui asperiores corrupti sed perspiciatis tempora id minus architecto!
● Rem beatae quos aut fugit vero.
● At adipisci enim id reiciendis officiis.
● Sed sapiente quia qui sint dolorem vel impedit magni.
In nesciunt quia qui asperiores corrupti sed perspiciatis tempora id minus architecto!
Rem beatae quos aut fugit vero.
At adipisci enim id reiciendis officiis.
Sed sapiente quia qui sint dolorem vel impedit magni.
Et dicta voluptatem sit fugit saepevel nulla et debitis iure et ipsa voluptas? Est facere harum
et inventore eveniet Aut rerum est molestias quam qui perspiciatis magnam.
Qui eligendi saepe et neque autem A omnis et pariatur rerum est dolore rerum est facere
Expand All @@ -94,16 +98,23 @@ pages:
explicabo. Et maxime assumenda et ipsam itaqueAut deleniti ut excepturi alias et fugit
facere non modi laudantium. Qui sapiente rerum non sunt ipsum Ad maxime est velit
eligendi aut quaerat officia est architecto magnam?
1. Et sequi ipsum et expedita ipsum eum dolore laborum.
2. Id enim unde eos commodi quidem et eius quaerat.
3. Est tempore veritatis sed aliquam Quis.
4. Qui quas tempora ut voluptates doloribus est facilis deserunt 33 distinctio internos.
1.
2.
3.
4. Et sequi ipsum et expedita ipsum eum dolore laborum.
Id enim unde eos commodi quidem et eius quaerat.
Est tempore veritatis sed aliquam Quis.
Qui quas tempora ut voluptates doloribus est facilis deserunt 33 distinctio internos.
markdown: |-
●
●
●
●
● Qui autem voluptas eum deserunt dolor.
● In nesciunt quia qui asperiores corrupti sed perspiciatis tempora id minus architecto!
● Rem beatae quos aut fugit vero.
● At adipisci enim id reiciendis officiis.
● Sed sapiente quia qui sint dolorem vel impedit magni.
In nesciunt quia qui asperiores corrupti sed perspiciatis tempora id minus architecto!
Rem beatae quos aut fugit vero.
At adipisci enim id reiciendis officiis.
Sed sapiente quia qui sint dolorem vel impedit magni.
Et dicta voluptatem sit fugit saepevel nulla et debitis iure et ipsa voluptas? Est facere harum
et inventore eveniet Aut rerum est molestias quam qui perspiciatis magnam.
Qui eligendi saepe et neque autem A omnis et pariatur rerum est dolore rerum est facere
Expand All @@ -114,7 +125,10 @@ pages:
explicabo. Et maxime assumenda et ipsam itaqueAut deleniti ut excepturi alias et fugit
facere non modi laudantium. Qui sapiente rerum non sunt ipsum Ad maxime est velit
eligendi aut quaerat officia est architecto magnam?
1. Et sequi ipsum et expedita ipsum eum dolore laborum.
2. Id enim unde eos commodi quidem et eius quaerat.
3. Est tempore veritatis sed aliquam Quis.
4. Qui quas tempora ut voluptates doloribus est facilis deserunt 33 distinctio internos.
1.
2.
3.
4. Et sequi ipsum et expedita ipsum eum dolore laborum.
Id enim unde eos commodi quidem et eius quaerat.
Est tempore veritatis sed aliquam Quis.
Qui quas tempora ut voluptates doloribus est facilis deserunt 33 distinctio internos.
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