<?php

class Pixel {
    function Pixel($r, $g, $b) 
    {
        $this->r = ($r > 255) ? 255 : (($r < 0) ? 0 : (int)($r));
        $this->g = ($g > 255) ? 255 : (($g < 0) ? 0 : (int)($g));
        $this->b = ($b > 255) ? 255 : (($b < 0) ? 0 : (int)($b));
    }
}

class Image_PixelOperations { 


    function pixelOperation(
            $input_image, 
            $output_image, 
            $operation_callback, 
            $factor = false
            ) 
    {

        $image = imagecreatefrompng($input_image);
        $x_dimension = imagesx($image);
        $y_dimension = imagesy($image);
        $new_image = imagecreatetruecolor($x_dimension, $y_dimension);

        if ($operation_callback == 'contrast') {
            $average_luminance = $this->getAverageLuminance($image);
        } else {
            $average_luminance = false;
        }

        for ($x = 0; $x < $x_dimension; $x++) {
            for ($y = 0; $y < $y_dimension; $y++) {

                $rgb = imagecolorat($image, $x, $y);
                $r = ($rgb >> 16) & 0xFF;
                $g = ($rgb >> 8) & 0xFF;
                $b = $rgb & 0xFF;

                $pixel = new Pixel($r, $g, $b);
                $pixel = call_user_func(
                    $operation_callback, 
                    $pixel, 
                    $factor, 
                    $average_luminance
                );

                $color = imagecolorallocate(
                    $image, 
                    $pixel->r, 
                    $pixel->g, 
                    $pixel->b
                );
                imagesetpixel($new_image, $x, $y, $color);
            }

        }

        imagepng($new_image, $output_image);
    }

    function addNoise($pixel, $factor)
    {
        $random = mt_rand(-$factor, $factor);
        return new Pixel(
                    $pixel->r + $random,
                    $pixel->g + $random,
                    $pixel->b + $random
                );
    }

    function adjustBrightness($pixel, $factor)
    {

        return new Pixel(
                    $pixel->r + $factor,
                    $pixel->g + $factor,
                    $pixel->b + $factor
                );
    }


    function swapColors($pixel, $factor) 
    {

        switch ($factor) {
            case 'rbg':
                return new Pixel(
                            $pixel->r,
                            $pixel->b,
                            $pixel->g
                        );
                break;
            case 'bgr':
                return new Pixel(
                            $pixel->b,
                            $pixel->g,
                            $pixel->r
                        );
                break;
            case 'brg':
                return new Pixel(
                            $pixel->b,
                            $pixel->r,
                            $pixel->g
                        );
                break;        
            case 'gbr':
                return new Pixel(
                            $pixel->g,
                            $pixel->b,
                            $pixel->r
                        );
                break;        
            case 'grb':
                return new Pixel(
                            $pixel->g,
                            $pixel->r,
                            $pixel->b
                        );
                break;        
            default:
                return $pixel;
        }

    }

    function removeColor($pixel, $factor) 
    {

        if ($factor == 'r' ) {
            $pixel->r = 0;
        }
        if ($factor == 'g' ) {
            $pixel->g = 0;
        }
        if ($factor == 'b' ) {
            $pixel->b = 0;
        }
        if ($factor == 'rb' || $factor == 'br') {
            $pixel->r = 0;
            $pixel->b = 0;
        }
        if ($factor == 'rg' || $factor == 'gr') {
            $pixel->r = 0;
            $pixel->g = 0;
        }
        if ($factor == 'bg' || $factor == 'gb') {
            $pixel->b = 0;
            $pixel->g = 0;
        }

        return $pixel;
    }

    function maxColor($pixel, $factor) 
    {

        if ($factor == 'r' ) {
            $pixel->r = 255;
        }
        if ($factor == 'g' ) {
            $pixel->g = 255;
        }
        if ($factor == 'b' ) {
            $pixel->b = 255;
        }
        if ($factor == 'rb' || $factor == 'br') {
            $pixel->r = 255;
            $pixel->b = 255;
        }
        if ($factor == 'rg' || $factor == 'gr') {
            $pixel->r = 255;
            $pixel->g = 255;
        }
        if ($factor == 'bg' || $factor == 'gb') {
            $pixel->b = 255;
            $pixel->g = 255;
        }

        return $pixel;
    }

    function negative($pixel) 
    {
        return new Pixel(
                    255 - $pixel->g,
                    255 - $pixel->r,
                    255 - $pixel->b
                );
    }

    function greyscale($pixel) 
    {

        $pixel_average = ($pixel->r + $pixel->g + $pixel->b) / 3;

        return new Pixel(
                    $pixel_average,
                    $pixel_average,
                    $pixel_average 
                );
    }

    function blackAndWhite($pixel, $factor) 
    {
        $pixel_total = ($pixel->r + $pixel->g + $pixel->b);

        if ($pixel_total > (((255 + $factor) / 2) * 3)) {
            // white
            $pixel->r = 255;
            $pixel->g = 255;
            $pixel->b = 255;
        } else {
            $pixel->r = 0;
            $pixel->g = 0;
            $pixel->b = 0;
        }

        return $pixel;
    }

    function clip($pixel, $factor)
    {
        if ($pixel->r > 255 - $factor) {
            $pixel->r = 255;
        }
        if ($pixel->r < $factor) {
            $pixel->r = 0;
        }
        if ($pixel->g > 255 - $factor) {
            $pixel->g = 255;
        }
        if ($pixel->g < $factor) {
            $pixel->g = 0;
        }
        if ($pixel->b > 255 - $factor) {
            $pixel->b = 255;
        }
        if ($pixel->b < $factor) {
            $pixel->b = 0;
        }

        return $pixel;
    }

    function getAverageLuminance($image) 
    {

        $luminance_running_sum = 0;
        
        $x_dimension = imagesx($image);
        $y_dimension = imagesy($image);

        for ($x = 0; $x < $x_dimension; $x++) {
            for ($y = 0; $y < $y_dimension; $y++) {

                $rgb = imagecolorat($image, $x, $y);
                $r = ($rgb >> 16) & 0xFF;
                $g = ($rgb >> 8) & 0xFF;
                $b = $rgb & 0xFF;

                $luminance_running_sum += (0.30 * $r) + (0.59 * $g) + (0.11 * $b);
                
            }

        }
       
        $total_pixels = $x_dimension * $y_dimension;

        return $luminance_running_sum / $total_pixels;
    }
    
    function contrast($pixel, $factor, $average_luminance) 
    {
        
        return new Pixel(
            $pixel->r * $factor + (1 - $factor) * $average_luminance,
            $pixel->g * $factor + (1 - $factor) * $average_luminance,
            $pixel->b * $factor + (1 - $factor) * $average_luminance
            );
    }
    
    function saltAndPepper($pixel, $factor) 
    {
        
        $black = (int)($factor/2 + 1);
        $white = (int)($factor/2 - 1);
        
        $random = mt_rand(0, $factor);
        
        $new_channel = false;
        
        if ($random == $black) {
            $new_channel = 0; 
        }
        if ($random == $white) {
            $new_channel = 255; 
        }
        
        if (is_int($new_channel)) {
        
            return new Pixel($new_channel, $new_channel, $new_channel);
            
        } else {
            return $pixel;
        }
    }

    function gamma($pixel, $factor) 
    {
        
        return new Pixel(
                pow($pixel->r / 255, $factor) * 255,
                pow($pixel->g / 255, $factor) * 255,
                pow($pixel->b / 255, $factor) * 255
            );
    }
    
    /**
     * @todo Revise the logic, there is something not quite right here
     *
     */
    function snap($pixel, $factor) 
    {

        $proximity = $factor[1];
        $snap_to = $factor[0];
        
        $close = (int)(255 * $proximity / 100);


        if ($pixel->r + $close >= 255 && $pixel->g + $close >= 255 && $pixel->b + $close >= 255) {
            return $pixel; //skip whitish
        }
        
    
        $rgb = array ('r', 'g', 'b');

        foreach ($rgb AS $channel) {
            if ($pixel->{$channel} < $snap_to->{$channel} && ($pixel->{$channel} + $close) > $snap_to->{$channel}) {
                $pixel->{$channel} = $snap_to->{$channel};
            }
            if ($pixel->{$channel} > $snap_to->{$channel} && ($pixel->{$channel} - $close) < $snap_to->{$channel}) {
                $pixel->{$channel} = $snap_to->{$channel};
            }
        }
       
        return $pixel;
        
    }
    
    /**
     *
     * @todo finish this method
     */
    function substitute($pixel, $factor) 
    {

        $find_pixel = $factor[0];
        $replace_with_pixel = $factor[1];
        $proximity = $factor[2];
        
        $close = (int)(255 * $proximity / 100);
        
        // to do
        
        return $pixel;
        
    }

    function randomizeOperation($pixel, $factor) 
    {

        $operations = array(
            'clip',
            'blackAndWhite',
            'greyscale',
            'negative',
            'maxColor',
            'removeColor',
            'swapColors',
            //'adjustBrightness', 
            'addNoise',
            //'contrast', //removed, too heavy for this purpose
            'saltAndPepper',
            'gamma',
        );
        $key = array_rand($operations);
        $operation = $operations[$key];

        switch ($operation) {
            case 'clip':
                $factor = mt_rand(0, 255);
                break;
            case 'maxColor':
            case 'removeColor':
                $factors = array('r', 'g', 'b', 'rg', 'rb', 'gb');
                $factor = $factors[array_rand($factors)];
                break;
            case 'swapColors':
                $factors = array('rbg', 'gbr', 'grb', 'bgr', 'brg');
                $factor = $factors[array_rand($factors)];
                break;
            case 'adjustBrightness':
                $factor = mt_rand(0, 255);
                break;
            case 'addNoise':
                $factor = mt_rand(0, 255);
                break;
            case 'saltAndPepper':
                $factor = mt_rand(0, 255);
                break;
            case 'gamma':
                $factor = mt_rand(0.5, 5);
                break;
            default:
                $factor = false;
                break;
        }

        return call_user_func(array($this, $operation), $pixel, $factor);

    }


}


if (!empty($_GET['image'])) {

    set_time_limit(60);

    $po =& new Image_PixelOperations();

    echo 'Original: <br /><img src="'. $_GET['image'] .'" />';
    echo '<hr />';

    // noise
    $noise = 500;
    $po->pixelOperation($_GET['image'], 'result_noise.png', array($po, 'addNoise'), $noise);
    echo '<br />Add noise (factor '. $noise .'): <br /><img src="result_noise.png" />';
    echo '<hr />';

    // 2 brightness adjustments
    $brightness = 50;
    $po->pixelOperation($_GET['image'], 'result_bright.png', array($po, 'adjustBrightness'), $brightness);
    echo '<br />Brighten: <br /><img src="result_bright.png" />';
    $brightness = -50;
    $po->pixelOperation($_GET['image'], 'result_dark.png', array($po, 'adjustBrightness'), $brightness);
    echo '<br />Darken: <br /><img src="result_dark.png" />';
    echo '<hr />';

    // 5 color swaps
    $po->pixelOperation($_GET['image'], 'result_rbg.png', array($po, 'swapColors'), 'rbg');
    echo '<br />RGB to RBG: <br /><img src="result_rbg.png" />';
    $po->pixelOperation($_GET['image'], 'result_bgr.png', array($po, 'swapColors'), 'bgr');
    echo '<br />RGB to BGR: <br /><img src="result_bgr.png" />';
    $po->pixelOperation($_GET['image'], 'result_brg.png', array($po, 'swapColors'), 'brg');
    echo '<br />RGB to BRG: <br /><img src="result_brg.png" />';
    $po->pixelOperation($_GET['image'], 'result_gbr.png', array($po, 'swapColors'), 'gbr');
    echo '<br />RGB to GBR: <br /><img src="result_gbr.png" />';
    $po->pixelOperation($_GET['image'], 'result_grb.png', array($po, 'swapColors'), 'grb');
    echo '<br />RGB to GRB: <br /><img src="result_grb.png" />';
    echo '<hr />';

    // 6 color removals
    $po->pixelOperation($_GET['image'], 'result_r.png', array($po, 'removeColor'), 'r');
    echo '<br />Remove red: <br /><img src="result_r.png" />';
    $po->pixelOperation($_GET['image'], 'result_g.png', array($po, 'removeColor'), 'g');
    echo '<br />Remove green: <br /><img src="result_g.png" />';
    $po->pixelOperation($_GET['image'], 'result_b.png', array($po, 'removeColor'), 'b');
    echo '<br />Remove blue: <br /><img src="result_b.png" />';
    $po->pixelOperation($_GET['image'], 'result_rg.png', array($po, 'removeColor'), 'rg');
    echo '<br />Remove red and green: <br /><img src="result_rg.png" />';
    $po->pixelOperation($_GET['image'], 'result_gb.png', array($po, 'removeColor'), 'gb');
    echo '<br />Remove green and blue: <br /><img src="result_gb.png" />';
    $po->pixelOperation($_GET['image'], 'result_rb.png', array($po, 'removeColor'), 'rb');
    echo '<br />Remove red and blue: <br /><img src="result_rb.png" />';
    echo '<hr />';

    // 6 color maximizations
    $po->pixelOperation($_GET['image'], 'result_maxr.png', array($po, 'maxColor'), 'r');
    echo '<br />Maximize red: <br /><img src="result_maxr.png" />';
    $po->pixelOperation($_GET['image'], 'result_maxg.png', array($po, 'maxColor'), 'g');
    echo '<br />Maximize green: <br /><img src="result_maxg.png" />';
    $po->pixelOperation($_GET['image'], 'result_maxb.png', array($po, 'maxColor'), 'b');
    echo '<br />Maximize blue: <br /><img src="result_maxb.png" />';
    $po->pixelOperation($_GET['image'], 'result_maxrg.png', array($po, 'maxColor'), 'rg');
    echo '<br />Maximize red and green: <br /><img src="result_maxrg.png" />';
    $po->pixelOperation($_GET['image'], 'result_maxgb.png', array($po, 'maxColor'), 'gb');
    echo '<br />Maximize green and blue: <br /><img src="result_maxgb.png" />';
    $po->pixelOperation($_GET['image'], 'result_maxrb.png', array($po, 'maxColor'), 'rb');
    echo '<br />Maximize red and blue: <br /><img src="result_maxrb.png" />';
    echo '<hr />';

    // negative
    $po->pixelOperation($_GET['image'], 'result_negative.png', array($po, 'negative'));
    echo '<br />Negative: <br /><img src="result_negative.png" />';
    echo '<hr />';

    // greyscale
    $po->pixelOperation($_GET['image'], 'result_grey.png', array($po, 'greyscale'));
    echo '<br />Greyscale: <br /><img src="result_grey.png" />';
    echo '<hr />';

    // B&W
    $bw = 20;
    $po->pixelOperation($_GET['image'], 'result_bw.png', array($po, 'blackAndWhite'), $bw); 
    echo '<br />Black and white (' . $bw . '): <br /><img src="result_bw.png" />';
    echo '<hr />';

    // clip
    $clip = 100;
    $po->pixelOperation($_GET['image'], 'result_clip.png', array($po, 'clip'), $clip); 
    echo '<br />Clip (' . $clip . '): <br /><img src="result_clip.png" />';
    echo '<hr />';

    // contrast
    $contrast = 0.5;
    $po->pixelOperation($_GET['image'], 'result_contrast1.png', array($po, 'contrast'), $contrast); 
    echo '<br />Contrast (' . $contrast . '): <br /><img src="result_contrast1.png" />';
    $contrast = 1.5;
    $po->pixelOperation($_GET['image'], 'result_contrast2.png', array($po, 'contrast'), $contrast); 
    echo '<br />Contrast (' . $contrast . '): <br /><img src="result_contrast2.png" />';
    echo '<hr />';
    
    // salt & pepper
    $probability = 20; 
    $po->pixelOperation($_GET['image'], 'result_sandp.png', array($po, 'saltAndPepper'), $probability); 
    echo '<br />Salt and Pepper (' . $probability . '): <br /><img src="result_sandp.png" />';
    echo '<hr />';

    // gamma
    $gamma = 2.2;
    $po->pixelOperation($_GET['image'], 'result_gamma.png', array($po, 'gamma'), $gamma); 
    echo '<br />Gamma (' . $gamma . '): <br /><img src="result_gamma.png" />';
    echo '<hr />';

    // random effect
    $po->pixelOperation($_GET['image'], 'result_rand.png', array($po, 'randomizeOperation')); 
    echo '<br />Random effect: <br /><img src="result_rand.png" />';



    // snap
    $snap_to = new Pixel(208, 122, 8); // dark blue - (2, 41, 107)
                                       // some orange - (208, 122, 8)
                                       // red - (255, 91, 60)
                                       // light blue - (100, 208, 249)
    $proximity = 80; // in %
    $po->pixelOperation($_GET['image'], 'result_snap.png', array($po, 'snap'), array($snap_to, $proximity)); 
    echo '<br /><span style="color: rgb('. $snap_to->r .','. $snap_to->g .','. $snap_to->b .')">Snap to color: </span><br /><img src="result_snap.png" />';
    echo '<hr />';

}
?>

<form method="get">
    <input name="image" />
    <input type="submit" />
</form>