From: Brion Vibber <brion@users.mediawiki.org>
Date: Tue, 29 Nov 2005 07:47:26 +0000 (+0000)
Subject: * Reduce fractions in display of exif exposure time
X-Git-Tag: 1.6.0~1098
X-Git-Url: https://git.cyclocoop.org/%7B%7B%20url_for%28?a=commitdiff_plain;h=7039d9bdd7127fca42efe54d4324489fab8b5dd7;p=lhc%2Fweb%2Fwiklou.git

* Reduce fractions in display of exif exposure time
---

diff --git a/RELEASE-NOTES b/RELEASE-NOTES
index 220afa5454..1e6349b8ed 100644
--- a/RELEASE-NOTES
+++ b/RELEASE-NOTES
@@ -261,6 +261,7 @@ fully support the editing toolbar, but was found to be too confusing.
 * (bug 4093) '&bot=1' in Special:Contributions now propagate to other links
 * Fix display of old recentchanges records for page moves
 * (bug 2111) Collapsable exif metadata table, clean up display
+* Reduce fractions in display of exif exposure time
 
 
 === Caveats ===
diff --git a/includes/Exif.php b/includes/Exif.php
index 8e71986952..9c3965a58e 100644
--- a/includes/Exif.php
+++ b/includes/Exif.php
@@ -998,7 +998,7 @@ class FormatExif {
 			case 'ExposureTime':
 				// Show the pretty fraction as well as decimal version
 				$tags[$tag] = wfMsg( 'exif-exposuretime-format',
-					$val, $this->formatNum( $val ) );
+					$this->formatFraction( $val ), $this->formatNum( $val ) );
 				break;
 			
 			case 'FNumber':
@@ -1053,4 +1053,52 @@ class FormatExif {
 		else
 			return $num;
 	}
+	
+	/**
+	 * Format a rational number, reducing fractions
+	 *
+	 * @access private
+	 *
+	 * @param mixed $num The value to format
+	 * @return mixed A floating point number or whatever we were fed
+	 */
+	function formatFraction( $num ) {
+		if ( preg_match( '/^(\d+)\/(\d+)$/', $num, $m ) ) {
+			$numerator = intval( $m[1] );
+			$denominator = intval( $m[2] );
+			$gcd = $this->gcd( $numerator, $denominator );
+			if( $gcd != 0 ) {
+				// 0 shouldn't happen! ;)
+				return $numerator / $gcd . '/' . $denominator / $gcd;
+			}
+		}
+		return $this->formatNum( $num );
+	}
+
+	/**
+	 * Calculate the greatest common divisor of two integers.
+	 *
+	 * @param int $a
+	 * @param int $b
+	 * @return int
+	 * @access private
+	 */
+	function gcd( $a, $b ) {
+		/*
+			// http://en.wikipedia.org/wiki/Euclidean_algorithm
+			// Recursive form would be:
+			if( $b == 0 )
+				return $a;
+			else
+				return gcd( $b, $a % $b );
+		*/
+		while( $b != 0 ) {
+			$remainder = $a % $b;
+			
+			// tail recursion...
+			$a = $b;
+			$b = $remainder;
+		}
+		return $a;
+	}
 }