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axeloz/Generate Image Placeholder

Last active September 17, 2024 12:52
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Revisions

  1. axeloz revised this gist Sep 17, 2024. 1 changed file with 1 addition and 1 deletion.
    2 changes: 1 addition & 1 deletion function.php
    View file
    Original file line number Diff line number Diff line change
    @@ -53,7 +53,7 @@ function generateImagePreview(String $file):String {
    case 6:
    $angle = 270;
    break;
    case 3:
    case 8:
    $angle = 90;
    break;
    }
  2. axeloz renamed this gist Jan 17, 2024. 1 changed file with 0 additions and 0 deletions.
    0 example.php → Generate Image Placeholder
    View file
    File renamed without changes.
  3. axeloz revised this gist Jan 17, 2024. 1 changed file with 8 additions and 0 deletions.
    8 changes: 8 additions & 0 deletions example.php
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    Original file line number Diff line number Diff line change
    @@ -5,6 +5,14 @@
    width="300"
    src="data:image/gif;base64,<?php echo generateImagePreview('./image/myimage.png'); ?>"
    />

    <!--
    THIS IS THE ACTUAL SIZE OF THE BASE64 USED TO DISPLAY THE IMAGE. SHORT ENOUGHT TO BE STORED INTO A DATABASE FIELD
    <img
    width="300"
    src="data:image/gif;base64,R0lGODdhBAACAKIAAJSanJyipKSenJSepJyWlKSipJSapKSmpCwAAAAABAACAAADBih1QTYgAQA7"
    />
    -->
    </body>

    </html>
  4. axeloz revised this gist Jan 17, 2024. No changes.
  5. axeloz revised this gist Jan 17, 2024. No changes.
  6. axeloz revised this gist Jan 17, 2024. No changes.
  7. axeloz created this gist Jan 17, 2024.
    10 changes: 10 additions & 0 deletions example.php
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,10 @@
    <html>

    <body>
    <img
    width="300"
    src="data:image/gif;base64,<?php echo generateImagePreview('./image/myimage.png'); ?>"
    />
    </body>

    </html>
    113 changes: 113 additions & 0 deletions function.php
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    Original file line number Diff line number Diff line change
    @@ -0,0 +1,113 @@
    <?php
    function generateImagePreview(String $file):String {
    // Supported image formats
    $mimetypes = [
    'image/jpeg' => [
    'mime' => 'image/jpeg',
    'function' => 'imagecreatefromjpeg',
    'extensions' => ['jpeg', 'jpg']
    ],
    'image/png' => [
    'function' => 'imagecreatefrompng',
    'extensions' => ['png']
    ],
    'image/webp' => [
    'function' => 'imagecreatefromwebp',
    'extensions' => ['webp']
    ],
    'image/gif' => [
    'function' => 'imagecreatefromgif',
    'extensions' => ['gif']
    ]
    ];

    // Checking that GD extension is enabled
    if (! extension_loaded('gd')) {
    throw new Exception('GD library is not installed on this instance');
    }

    // Reading EXIF data
    if ($exif = exif_read_data($file)) {
    $type = $exif['MimeType'] ?? null;
    }

    // Getting correct function to use
    $function = $mimetypes[$type]['function'] ?? null;
    if (empty($function) || ! is_callable($function) || ! function_exists($function)) {
    throw new Exception('This image format is not supported');
    }

    // Calling the function
    if (false === $gd = call_user_func($function, $file)) {
    throw new Exception('Unable to generate a GD image from source');
    }

    // Does this image needs to be rotated or flipped?
    if (! empty($exif['Orientation']) && $exif['Orientation'] !== 1) {
    // It's a rotate
    if (in_array($exif['Orientation'], [3, 6, 8])) {
    switch ($exif['Orientation']) {
    case 3:
    $angle = 180;
    break;
    case 6:
    $angle = 270;
    break;
    case 3:
    $angle = 90;
    break;
    }

    if (false === $gd = imagerotate($gd, $angle, 0)) {
    // Should we block the preview generation because this image is not rotated?
    }
    }
    // It's a flip
    else {
    switch ($exif['Orientation']) {
    case 2:
    $flip = IMG_FLIP_HORIZONTAL;
    break;
    case 4:
    $flip = IMG_FLIP_VERTICAL;
    break;
    case 5:
    $flip = IMG_FLIP_BOTH;
    break;
    }

    if (false === $gd = imageflip($gd, $flip)) {
    // Should we block the preview generation because this image is not rotated?
    }
    }
    }

    // First we generate the new image sizes
    $max_width = 4;
    $width = imagesx($gd);
    $height = imagesy($gd);
    $ratio = $width / $height;
    $max_height = max(round($max_width, 1) / $ratio, 1);

    // Then we create a new image with correct size and ratio
    if (false === $temp = imagecreatetruecolor($max_width, $max_height)) {
    throw new Exception('Cannot create a new image container');
    }

    // Finally we copy the original image to the new container image
    if (false === imagecopyresampled($temp, $gd, 0, 0, 0, 0, $max_width, $max_height, $width, $height)) {
    throw new Exception('Cannot resample image');
    }

    // Adding blur and smoothing
    imagefilter($temp, IMG_FILTER_GAUSSIAN_BLUR);
    imagefilter($temp, IMG_FILTER_SMOOTH, IMG_FILTER_SMOOTH);

    // Outputting image to GIF format
    ob_start();
    imagegif($temp);
    $image = ob_get_contents();
    ob_end_clean();

    return base64_encode($image);
    }