Added calculateTextWidth function to Font (#517)

* Added calculateTextWidth function to Font Character width is read from font details field 'Widths'. * Refined example in Usage.md * Added parameter types Co-authored-by: Konrad Abicht <hi@inspirito.de>
smalot · Mar 21, 2022 · ef70983 · ef70983
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diff --git a/doc/Usage.md b/doc/Usage.md
@@ -153,3 +153,17 @@ $pdf = $parser->parseContent(base64_decode($base64PDF));
 $text = $pdf->getText();
 echo $text;
 ```
+
+## Calculate text width
+
+Try to calculate text width for given font.
+Characters without width are added to `$missing` array in second parameter.
+
+```php
+$parser = new \Smalot\PdfParser\Parser();
+$pdf = $parser->parseFile('document.pdf');
+// get first font (we assume here there is at least one)
+$font = reset($pdf->getFonts());
+// get width
+$width = $font->calculateTextWidth('Some text', $missing);
+```
diff --git a/src/Smalot/PdfParser/Font.php b/src/Smalot/PdfParser/Font.php
@@ -267,6 +267,38 @@ public function setTable(array $table)
         $this->table = $table;
     }
 
+    /**
+     * Calculate text width with data from header 'Widths'. If width of character is not found then character is added to missing array.
+     */
+    public function calculateTextWidth(string $text, array &$missing = null): ?float
+    {
+        $index_map = array_flip($this->table);
+        $details = $this->getDetails();
+        $widths = $details['Widths'];
+
+        // Widths array is zero indexed but table is not. We must map them based on FirstChar and LastChar
+        $width_map = array_flip(range($details['FirstChar'], $details['LastChar']));
+
+        $width = null;
+        $missing = [];
+        $textLength = mb_strlen($text);
+        for ($i = 0; $i < $textLength; ++$i) {
+            $char = mb_substr($text, $i, 1);
+            if (
+                !\array_key_exists($char, $index_map)
+                || !\array_key_exists($index_map[$char], $width_map)
+                || !\array_key_exists($width_map[$index_map[$char]], $widths)
+            ) {
+                $missing[] = $char;
+                continue;
+            }
+            $width_index = $width_map[$index_map[$char]];
+            $width += $widths[$width_index];
+        }
+
+        return $width;
+    }
+
     /**
      * Decode hexadecimal encoded string. If $add_braces is true result value would be wrapped by parentheses.
      */

diff --git a/tests/Integration/FontTest.php b/tests/Integration/FontTest.php
@@ -410,4 +410,25 @@ public function testEncodingWithoutBaseEncoding(): void
         $font->setTable([]);
         $this->assertEquals('?', $font->translateChar('a'));
     }
+
+    public function testCalculateTextWidth(): void
+    {
+        $filename = $this->rootDir.'/samples/Document1_pdfcreator_nocompressed.pdf';
+        $parser = $this->getParserInstance();
+        $document = $parser->parseFile($filename);
+        $fonts = $document->getFonts();
+
+        $font = $fonts['7_0'];
+        $widths = $font->getDetails()['Widths'];
+        $this->assertEquals($widths[0], $font->calculateTextWidth('D'));
+        $this->assertEquals($widths[10], $font->calculateTextWidth('l'));
+
+        $width = $font->calculateTextWidth('Calibri', $missing);
+        $this->assertEquals(936, $width);
+        $this->assertEquals(['C', 'a', 'b', 'r'], $missing);
+
+        $width = $fonts['9_0']->calculateTextWidth('Calibri', $missing);
+        $this->assertEquals(2573, $width);
+        $this->assertEquals([], $missing);
+    }
 }