imagecolorallocate - PHP code example

The php Function Imagecolorallocate

The php function imagecolorallocate is one of the fundamental functions used in PHP GD (Graphics Datatype) library. PHP GD is an advanced image manipulation library that is built into the PHP engine and provides a powerful way to dynamically draw and manipulate images within your web pages. The GD library also allows you to create GIF, JPEG and PNG files with alpha transparency.

For the purposes of this article we will be using an existing PNG file as our canvas and we will be focusing on the GD functions that allow you to draw lines and other shapes. First you will need to have the GD library installed on your system. This can usually be done by your host or by installing the GD library manually.

In the following example we will be drawing a line between two points on the image. The first point will be 30 pixels from the left edge of the image and the second point will be 165 pixels from that same edge. The line color will be a shade of green that we have previously created with the imagecolorallocate() function.

In order to do this you will need to pass the following parameters to the imageline() function:

imagecolorallocate example

    private function createNewImage($image, array $originalSize, array $newSize, string $extension)
    {
        // Creates a new image with given size         $newImage = imagecreatetruecolor($newSize['width'], $newSize['height']);
        if ($newImage === false) {
            throw new RuntimeException('Could not create image');
        }

        if (\in_array($extension, ['jpg', 'jpeg'])) {
            $background = (int) imagecolorallocate($newImage, 255, 255, 255);
            imagefill($newImage, 0, 0, $background);
        } else {
            // Disables blending             imagealphablending($newImage, false);
        }
        // Saves the alpha information         imagesavealpha($newImage, true);
        // Copies the original image into the new created image with re-sampling         imagecopyresampled(
            $newImage,
            $image,

if ($im === false) {
            throw new RuntimeException('Could not create captcha image');
        }

        if (!empty($this->config->get('CaptchaColor'))) {
            $colors = explode(',', $this->config->get('CaptchaColor'));
        } else {
            $colors = explode(',', '255,0,0');
        }

        $black = (int) imagecolorallocate($im, (int) $colors[0], (int) $colors[1], (int) $colors[2]);

        $string = implode(' ', str_split($string));

        if (!empty($font)) {
            for ($i = 0, $iMax = \strlen($string); $i < $iMax; ++$i) {
                $rand1 = Random::getInteger(35, 40);
                $rand2 = Random::getInteger(15, 20);
                $rand3 = Random::getInteger(60, 70);
                imagettftext($im, $rand1, $rand2, ($i + 1) * 15, $rand3, $black, $font, $string[$i]);
                imagettftext($im, $rand1, $rand2, (($i + 1) * 15) + 2, $rand3 + 2, $black, $font, $string[$i]);
            }

          $fill_color = imagecolorallocatealpha($res, 255, 255, 255, 127);
        }
        else {
          $fill_rgb = Color::hexToRgb($arguments['transparent_color']);
          $fill_color = imagecolorallocatealpha($res, $fill_rgb['red'], $fill_rgb['green'], $fill_rgb['blue'], 127);
          imagecolortransparent($res, $fill_color);
        }
        imagefill($res, 0, 0, $fill_color);
        break;

      case IMAGETYPE_JPEG:
        imagefill($res, 0, 0, imagecolorallocate($res, 255, 255, 255));
        break;

    }

    // Update the toolkit properties.     $this->getToolkit()->setType($type);
    $this->getToolkit()->setResource($res);

    // Destroy the original resource if it is not needed by other operations.     if (!$arguments['is_temp'] && is_resource($original_res)) {
      imagedestroy($original_res);
    }

    private function createNewImage(\GdImage $mediaImage, MediaType $type, array $originalImageSize, array $thumbnailSize): \GdImage
    {
        $thumbnail = imagecreatetruecolor($thumbnailSize['width'], $thumbnailSize['height']);

        if ($thumbnail === false) {
            throw MediaException::cannotCreateImage();
        }

        if (!$type->is(ImageType::TRANSPARENT)) {
            $colorWhite = (int) imagecolorallocate($thumbnail, 255, 255, 255);
            imagefill($thumbnail, 0, 0, $colorWhite);
        } else {
            imagealphablending($thumbnail, false);
        }

        imagesavealpha($thumbnail, true);
        imagecopyresampled(
            $thumbnail,
            $mediaImage,
            0,
            0,

/** @var \Drupal\Core\Render\RendererInterface $renderer */
    $renderer = $this->container->get('renderer');

    $png = File::create([
      'uri' => 'public://test-image.png',
    ]);
    $png->save();

    // We need to create an actual empty PNG, or the GD toolkit will not     // consider the image valid.     $png_resource = imagecreate(300, 300);
    imagefill($png_resource, 0, 0, imagecolorallocate($png_resource, 0, 0, 0));
    imagepng($png_resource, $png->getFileUri());

    $svg = File::create([
      'uri' => 'public://test-image.svg',
    ]);
    $svg->save();
    // We don't have to put any real SVG data in here, because the GD toolkit     // won't be able to load it anyway.     touch($svg->getFileUri());

    $entity = EntityTest::create([

    protected function _rotate(int $angle): bool
    {
        // Create the image handle         $srcImg = $this->createImage();

        // Set the background color         // This won't work with transparent PNG files so we are         // going to have to figure out how to determine the color         // of the alpha channel in a future release.
        $white = imagecolorallocate($srcImg, 255, 255, 255);

        // Rotate it!         $destImg = imagerotate($srcImg, $angle, $white);

        // Kill the file handles         imagedestroy($srcImg);

        $this->resource = $destImg;

        return true;
    }

public function image($destination, $min_resolution, $max_resolution) {
    $extension = pathinfo($destination, PATHINFO_EXTENSION);
    $min = explode('x', $min_resolution);
    $max = explode('x', $max_resolution);

    $width = rand((int) $min[0], (int) $max[0]);
    $height = rand((int) $min[1], (int) $max[1]);

    // Make an image split into 4 sections with random colors.     $im = imagecreate($width, $height);
    for ($n = 0; $n < 4; $n++) {
      $color = imagecolorallocate($im, rand(0, 255), rand(0, 255), rand(0, 255));
      $x = $width / 2 * ($n % 2);
      $y = $height / 2 * (int) ($n >= 2);
      imagefilledrectangle($im, (int) $x, (int) $y, (int) ($x + $width / 2), (int) ($y + $height / 2), $color);
    }

    // Make a perfect circle in the image middle.     $color = imagecolorallocate($im, rand(0, 255), rand(0, 255), rand(0, 255));
    $smaller_dimension = min($width, $height);
    imageellipse($im, (int) ($width / 2), (int) ($height / 2), $smaller_dimension, $smaller_dimension, $color);

    $save_function = 'image' . ($extension == 'jpg' ? 'jpeg' : $extension);

        $code = $this->createCaptchaCode($length);

        $filesystem = new Filesystem();

        if ($filesystem->exists($this->backgroundPath)) {
            /** @var \GdImage $img */
            $img = imagecreatefrompng($this->backgroundPath);
        } else {
            /** @var \GdImage $img */
            $img = imagecreate(self::FALLBACK_WIDTH_IMAGE, self::FALLBACK_HEIGHT_IMAGE);
            imagecolorallocate($img, 255, 255, 255);
        }

        $codeColor = (int) imagecolorallocate($img, 0, 0, 0);
        if ($filesystem->exists($this->fontPath)) {
            imagettftext($img, 45, 0, 80, 55, $codeColor, $this->fontPath, $code);
        } else {
            imagestring($img, 5, 100, 20, $code, $codeColor);
        }

        ob_start();
        imagepng($img, null, 9);

if ($stm->rowCount()) {
            $sql = 'UPDATE s_campaigns_mailings SET `read`=`read`+1 WHERE id=?';
            Shopware()->Db()->query($sql, [$mailing]);
        }

        $this->Response()->headers->set('content-type', 'image/gif');
        $image = imagecreate(1, 1);
        if ($image === false) {
            return;
        }
        $white = (int) imagecolorallocate($image, 255, 255, 255);
        imagefill($image, 1, 1, $white);
        imagegif($image);
        imagedestroy($image);
    }

    /** * @deprecated in 5.6, will be private in 5.8 * * Init mailing method * * Initializes the mailing using the mailing id. * * @param int|null $mailingID * * @return array|null */