<?php
/*
        this function intends to reduce the size of image and not for enlargement
        action will be aborted if target file is larger the source
        tested with PHP Version 7.0.13
*/
function resize($image, $thumb, $option = 'maxwidth', $dimension = array('200')) {
    $methods = [
                            IMAGETYPE_GIF => ['imagegif','imagecreatefromgif'],
                            IMAGETYPE_JPEG => ['imagejpeg','imagecreatefromjpeg'],
                            IMAGETYPE_PNG => ['imagepng','imagecreatefrompng'],
                            ];

    $options = ['maxwidth','maxheight','contain','cover'];
    if (!in_array($option, $options)) {
        return $logs[] = 'Option Not Defined: maxwidth | maxheight | content | cover. Action aborted';
    }

    if ($option == 'contain' || $option == 'cover') {
        if (!is_array($dimension) || count($dimension) < 2) {
            return $logs[] = 'Dimensions Not Defined: [width, height]. Action aborted';
        }
    }

    list($source_image_width, $source_image_height, $source_image_type) = getimagesize($image);
    $extension = pathinfo($image)['extension'];
    if (
            ($extension == 'image/gif' && $cource_image_type != IMAGETYPE_GIF) ||
            ($extension == 'image/jpg' && $cource_image_type != IMAGETYPE_JPEG) ||
            ($extension == 'image/png' && $cource_image_type != IMAGETYPE_PNG)
            ) {
                return $logs[] = "File extension and file type mismatch. Action aborted";
    }

    if (($option == 'maxwidth' && $source_image_width < $dimension[0])  || ($option == 'maxheight' && $source_image_height < $dimension[0])) {
        return $logs[] = "Target file is larger than source file. Action aborted";
    }

    if (pathinfo($image)['extension'] != pathinfo($thumb)['extension']) {
        return $logs[] = "Target file extension mismatch. Action aborted";
    }
    $ratio = $source_image_height / $source_image_width;

    switch ($option) {
        case 'maxwidth':
            $thumbwidth = $dimension[0];
            $thumbheight = $thumbwidth * $ratio;
        break;
        case 'maxheight':
            $thumbheight = $dimension[0];
            $thumbwidth = $thumbheight / $ratio;
        break;
        case 'contain':
            $thumbwidth = $dimension[0];
            $thumbheight = $thumbwidth * $ratio;
            if ($thumbheight > $dimension[1]) {
                $thumbheight = $dimension[1];
                $thumbwidth = $thumbheight / $ratio;
            }
        break;
        case 'cover':
            if ($dimension[0] > $dimension[1]) {
                $thumbwidth = $dimension[0];
                $thumbheight = $thumbwidth * $ratio;
            } else {
                $thumbheight = $dimension[1];
                $thumbwidth = $thumbheight / $ratio;
            }
        break;
        default:
            $thumbwidth = $dimension[0];
            $thumbheight = $thumbwidth * $ratio;
        break;
    }

    $temp_thumb = imagecreatetruecolor($thumbwidth, $thumbheight);
    /* $methods indexes based on IMAGETYPE_XXX constants */

    if (!$temp_source = $methods[$source_image_type][1]($image)) { $logs[] = $methods[$source_image_type][1] . 'failure: ' . $image; }
    switch ($source_image_type) {
        case IMAGETYPE_GIF:
        $transparency = imagecolorallocatealpha($temp_thumb, 255, 255, 255, 127);
        imagefilledrectangle($temp_thumb, 0, 0, $thumbwidth, $thumbheight, $transparency);
        break;
        case IMAGETYPE_JPEG:
        break;
        case IMAGETYPE_PNG:
        imagealphablending($temp_thumb, false);
        imagesavealpha($temp_thumb,true);
        $transparency = imagecolorallocatealpha($temp_thumb, 255, 255, 255, 127);
        imagefilledrectangle($temp_thumb, 0, 0, $thumbwidth, $thumbheight, $transparency);
        break;
        default:
        $logs[] = "Unknown type: {$image}";
        break;
    }

    imagecopyresampled($temp_thumb, $temp_source, 0, 0, 0, 0, $thumbwidth, $thumbheight, $source_image_width, $source_image_height);

    if ($option == 'cover') {
        /* calculate offset-x and offset-y for center crop */
        $x = (imagesx($temp_thumb) - $dimension[0]) / 2;
        $y = (imagesy($temp_thumb) - $dimension[1]) / 2;
        $x = ($x > 0)? $x : 0; /* probably don't need this */
        $y = ($y > 0)? $y : 0; /* probably don't need this */
        $temp_thumb = imagecrop($temp_thumb, ['x' => $x, 'y' => $y, 'width' => $dimension[0], 'height' => $dimension[1]]);
    }

    if (!$methods[$source_image_type][0]($temp_thumb,$thumb, 9)) { $logs[] = "Unable to create thumb from temp image of ${image}"; }
    if (!imagedestroy($temp_thumb)) { $log[] = "Unable to destroy temp file for {$image}"; }
    imagedestroy($temp_source);
    return (!empty($logs))? $logs : true;
}
?>
<!DOCTYPE html>
<html>
    <head>
        <style>
            .box {
                display: flex;
                align-items: center;
                justify-content: center;
                width: 200px;
                height: 400px;
                border: 1px solid purple;
            }
        </style>
    </head>
    <body>
<?php
    $source_files = ['test.gif','test.png','test.jpg'];
    $dimension = [200, 400];
    foreach ($source_files as $file) {
        $option = 'cover';
        $target_file = 'upload/'.$option.'_'.$file;
        if ($result = resize('upload/' . $file, $target_file, $option, $dimension)) {
            echo '<div class="box"><img src="'.$target_file.'"></div>';
        } else {
            echo '<div class="box">'.implode($result).'</div>';
        }
    }
    echo '<br>';
    foreach ($source_files as $file) {
        $option = 'contain';
        $target_file = 'upload/'.$option.'_'.$file;
        if ($result = resize('upload/' . $file, $target_file, $option, $dimension)) {
            echo '<div class="box"><img src="'.$target_file.'"></div>';
        } else {
            echo '<div class="box">'.implode($result).'</div>';
        }
    }
    echo '<br>';
    foreach ($source_files as $file) {
        $option = 'maxwidth';
        $target_file = 'upload/'.$option.'_'.$file;
        if ($result = resize('upload/' . $file, $target_file, $option, [$dimension[0]])) {
            echo '<div class="box"><img src="'.$target_file.'"></div>';
        } else {
            echo '<div class="box">'.implode($result).'</div>';
        }
    }
    echo '<br>';
    foreach ($source_files as $file) {
        $option = 'maxheight';
        $target_file = 'upload/'.$option.'_'.$file;
        if ($result = resize('upload/' . $file, $target_file, $option, [$dimension[1]])) {
            echo '<div class="box"><img src="'.$target_file.'"></div>';
        } else {
            echo '<div class="box">'.implode($result).'</div>';
        }
    }
?>
    </body>
</html>