sunnysideup / silverstripe-assets_overview

src/Api/CompareImages.php

<?php

namespace Sunnysideup\AssetsOverview\Api;

class CompareImages
{
    public function compare($a, $b)
    {
        // main function. returns the hammering distance of two images' bit value
        $i1 = $this->createImage($a);
        $i2 = $this->createImage($b);

        if (! $i1 || ! $i2) {
            return false;
        }

        $i1 = $this->resizeImage($i1, $a);
        $i2 = $this->resizeImage($i2, $b);

        imagefilter($i1, IMG_FILTER_GRAYSCALE);
        imagefilter($i2, IMG_FILTER_GRAYSCALE);

        $colorMean1 = $this->colorMeanValue($i1);
        $colorMean2 = $this->colorMeanValue($i2);

        $bits1 = $this->bits($colorMean1);
        $bits2 = $this->bits($colorMean2);

        $hammeringDistance = 0;

        for ($a = 0; $a < 64; ++$a) {
            if ($bits1[$a] !== $bits2[$a]) {
                ++$hammeringDistance;
            }
        }

        return $hammeringDistance;
    }

    private function mimeType($i)
    {
        // returns array with mime type and if its jpg or png. Returns false if it isn't jpg or png
        $mime = getimagesize($i);
        $return = [$mime[0], $mime[1]];

        switch ($mime['mime']) {
            case 'image/jpeg':
                $return[] = 'jpg';

                return $return;
            case 'image/png':
                $return[] = 'png';

                return $return;
            default:
                return false;
        }
    }

    private function createImage($i)
    {
        // retuns image resource or false if its not jpg or png
        $mime = $this->mimeType($i);

        if ('jpg' === $mime[2]) {
            return imagecreatefromjpeg($i);
        }

        if ('png' === $mime[2]) {
            return imagecreatefrompng($i);
        }

        return false;
    }

    private function resizeImage($i, $source)

The parameter $i is not used and could be removed.

    {
        // resizes the image to a 8x8 squere and returns as image resource
        $mime = $this->mimeType($source);

        $t = imagecreatetruecolor(8, 8);

        $source = $this->createImage($source);

        imagecopyresized($t, $source, 0, 0, 0, 0, 8, 8, $mime[0], $mime[1]);

It seems like $source can also be of type false; however, parameter $src_image of imagecopyresized() does only seem to accept GdImage|resource, maybe add an additional type check?

        return $t;
    }

    private function colorMeanValue($i)
    {
        // returns the mean value of the colors and the list of all pixel's colors
        $colorList = [];
        $colorSum = 0;
        for ($a = 0; $a < 8; ++$a) {
            for ($b = 0; $b < 8; ++$b) {
                $rgb = imagecolorat($i, $a, $b);
                $colorList[] = $rgb & 0xFF;
                $colorSum += $rgb & 0xFF;
            }
        }

        return [$colorSum / 64, $colorList];
    }

    private function bits($colorMean)
    {
        // returns an array with 1 and zeros. If a color is bigger than the mean value of colors it is 1
        $bits = [];

        foreach ($colorMean[1] as $color) {
            $bits[] = $color >= $colorMean[0] ? 1 : 0;
        }

        return $bits;
    }
}