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Logic fix (undefined variables in the loop), and recommendation of scjr's response over my own.

edited May 6, 2013 at 14:55

Note: I seriously recommend scjr's response over my own. His code implements all of my (minor) adjustments, but also includes the improved coding practices, organization, and straightforward logic that good code should have.

Making it more functional and adjusting the variable names helps make it more readable and helps you more quickly identify what each part of code does what.

<?php function findSimilarityBetweenImages($imagePathA, $imagePathB, $accuracy){ //if images are png $imageA = imagecreatefrompng($imagePathA); $imageB = imagecreatefrompng($imagePathB); //if images are jpeg //$imageA = imagecreatefromjpeg($imagePathA); //$imageB = imagecreatefromjpeg($imagePathB); //get image resolution $imageWidth = imagesx($imageA); $imageHeight = imagesy($imageA); $density = $accuracy * 5; $xIncrement = round($imageWidth/$density); $yIncrement = round($imageHeight/$density); //Compare the color of each point while looping through. $matchingPoints = 0; for ($y=0; $y < $pointsHeight;$density; $y++) { for ($x=0; $x < $pointsWidth;$density; $x++){ $colorsa = colorData($imageA, $x*$xIncrement, $y*$yIncrement); $colorsb = colorData($imageB, $x*$xIncrement, $y*$yIncrement); if(colorsMatch($colorsa, $colorsb)){ $matchingPoints++; //Match between points. } } } $totalPoints = $pointsHeight * $pointsWidth;$imageHeight; //A similarity or percentage of match between the two images. $similarity = $matchingPoints*(100/$totalPoints); return $similarity; } function colorData($imageA, $x, $y){ $rgb = imagecolorat($imageA, $x, $y); return imagecolorsforindex($imageA, $rgb); } function colorsMatch($colorsa, $colorsb){ //Compare the R, G, and B values return colorComp($colorsa['red'], $colorsb['red']) && colorComp($colorsa['green'], $colorsb['green']) && colorComp($colorsa['blue'], $colorsb['blue']); } function colorComp($color, $c){ //To see if the points match return ($color >= $c-2 && $color <= $c+2); } ?>

Making it more functional and adjusting the variable names helps make it more readable and helps you more quickly identify what each part of code does what.

<?php function findSimilarityBetweenImages($imagePathA, $imagePathB, $accuracy){ //if images are png $imageA = imagecreatefrompng($imagePathA); $imageB = imagecreatefrompng($imagePathB); //if images are jpeg //$imageA = imagecreatefromjpeg($imagePathA); //$imageB = imagecreatefromjpeg($imagePathB); //get image resolution $imageWidth = imagesx($imageA); $imageHeight = imagesy($imageA); $density = $accuracy * 5; $xIncrement = round($imageWidth/$density); $yIncrement = round($imageHeight/$density); //Compare the color of each point while looping through. $matchingPoints = 0; for ($y=0; $y < $pointsHeight; $y++) { for($x=0; $x < $pointsWidth; $x++){ $colorsa = colorData($imageA, $x*$xIncrement, $y*$yIncrement); $colorsb = colorData($imageB, $x*$xIncrement, $y*$yIncrement); if(colorsMatch($colorsa, $colorsb)){ $matchingPoints++; //Match between points. } } } $totalPoints = $pointsHeight * $pointsWidth; //A similarity or percentage of match between the two images. $similarity = $matchingPoints*(100/$totalPoints); return $similarity; } function colorData($imageA, $x, $y){ $rgb = imagecolorat($imageA, $x, $y); return imagecolorsforindex($imageA, $rgb); } function colorsMatch($colorsa, $colorsb){ //Compare the R, G, and B values return colorComp($colorsa['red'], $colorsb['red']) && colorComp($colorsa['green'], $colorsb['green']) && colorComp($colorsa['blue'], $colorsb['blue']); } function colorComp($color, $c){ //To see if the points match return ($color >= $c-2 && $color <= $c+2); } ?>

Making it more functional and adjusting the variable names helps make it more readable and helps you more quickly identify what each part of code does what.

<?php function findSimilarityBetweenImages($imagePathA, $imagePathB, $accuracy){ //if images are png $imageA = imagecreatefrompng($imagePathA); $imageB = imagecreatefrompng($imagePathB); //if images are jpeg //$imageA = imagecreatefromjpeg($imagePathA); //$imageB = imagecreatefromjpeg($imagePathB); //get image resolution $imageWidth = imagesx($imageA); $imageHeight = imagesy($imageA); $density = $accuracy * 5; $xIncrement = round($imageWidth/$density); $yIncrement = round($imageHeight/$density); //Compare the color of each point while looping through. $matchingPoints = 0; for ($y=0; $y < $density; $y++) { for ($x=0; $x < $density; $x++){ $colorsa = colorData($imageA, $x*$xIncrement, $y*$yIncrement); $colorsb = colorData($imageB, $x*$xIncrement, $y*$yIncrement); if(colorsMatch($colorsa, $colorsb)){ $matchingPoints++; //Match between points. } } } $totalPoints = $pointsHeight * $imageHeight; //A similarity or percentage of match between the two images. $similarity = $matchingPoints*(100/$totalPoints); return $similarity; } function colorData($imageA, $x, $y){ $rgb = imagecolorat($imageA, $x, $y); return imagecolorsforindex($imageA, $rgb); } function colorsMatch($colorsa, $colorsb){ //Compare the R, G, and B values return colorComp($colorsa['red'], $colorsb['red']) && colorComp($colorsa['green'], $colorsb['green']) && colorComp($colorsa['blue'], $colorsb['blue']); } function colorComp($color, $c){ //To see if the points match return ($color >= $c-2 && $color <= $c+2); } ?>

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answered May 1, 2013 at 15:26

The Pattern in Pi

Making it more functional and adjusting the variable names helps make it more readable and helps you more quickly identify what each part of code does what.

TotalPoints can be calculated, and doesn't belong in the loop. I combined x, i, n, and y, to clean up the loops as well. They could be adjusted even more, changing x++ to x+=xIncrement, removing the need to multiply x and y at every point (a performance hit that I introduced that you could remove).

<?php function findSimilarityBetweenImages($imagePathA, $imagePathB, $accuracy){ //if images are png $imageA = imagecreatefrompng($imagePathA); $imageB = imagecreatefrompng($imagePathB); //if images are jpeg //$imageA = imagecreatefromjpeg($imagePathA); //$imageB = imagecreatefromjpeg($imagePathB); //get image resolution $imageWidth = imagesx($imageA); $imageHeight = imagesy($imageA); $density = $accuracy * 5; $xIncrement = round($imageWidth/$density); $yIncrement = round($imageHeight/$density); //Compare the color of each point while looping through. $matchingPoints = 0; for ($y=0; $y < $pointsHeight; $y++) { for($x=0; $x < $pointsWidth; $x++){ $colorsa = colorData($imageA, $x*$xIncrement, $y*$yIncrement); $colorsb = colorData($imageB, $x*$xIncrement, $y*$yIncrement); if(colorsMatch($colorsa, $colorsb)){ $matchingPoints++; //Match between points. } } } $totalPoints = $pointsHeight * $pointsWidth; //A similarity or percentage of match between the two images. $similarity = $matchingPoints*(100/$totalPoints); return $similarity; } function colorData($imageA, $x, $y){ $rgb = imagecolorat($imageA, $x, $y); return imagecolorsforindex($imageA, $rgb); } function colorsMatch($colorsa, $colorsb){ //Compare the R, G, and B values return colorComp($colorsa['red'], $colorsb['red']) && colorComp($colorsa['green'], $colorsb['green']) && colorComp($colorsa['blue'], $colorsb['blue']); } function colorComp($color, $c){ //To see if the points match return ($color >= $c-2 && $color <= $c+2); } ?>