imageistruecolor - PHP code example

The php Function Imageistruecolor

php function imageistruecolor is one of the basic and most useful functions available in php. It is used to find whether an image is a true color or not. It is important to know that a true color image has an unlimited number of colors. This is different from the limited number of colors that a palette based image can have.

The function works by passing the image through a series of filters. These filters are designed to change the pixel values of the image to specific colors. Once the filtering has been completed, the final result is a true color image.

In order to use this php function, you will need to have the GD library activated on your server/host. The GD library is the most popular tool for dynamic creation and manipulation of images in php. It is included with most php installations and should be active by default.

This code will create a 300x200 pixels true color image. It starts by allocating a red color using the imagecolorallocate() function. The image is then filled with the color using the imagefilledrectangle() function. Finally the text 'Hello World!' is added to the image at position (250,150).

I created this php function because I wanted to get rid of the 'antialias' lines that you sometimes see in gif images. This can be caused by various things, such as compression level and color settings. This function will eliminate the aliasing in almost all cases by making the image true color, thereby reducing its file size without sacrificing quality.

imageistruecolor example

  public function testManipulations(string $file_name, string $test_case, string $operation, array $arguments, array $expected): void {
    // Load up a fresh image.     $image = $this->imageFactory->get('core/tests/fixtures/files/' . $file_name);
    $toolkit = $image->getToolkit();
    $this->assertTrue($image->isValid());
    $image_original_type = $image->getToolkit()->getType();

    $this->assertTrue(imageistruecolor($toolkit->getResource()), "Image '$file_name' after load should be a truecolor image, but it is not.");

    // Perform our operation.     $image->apply($operation, $arguments);

    // Flush Image object to disk storage.     $file_path = $this->directory . '/' . $test_case . image_type_to_extension($image->getToolkit()->getType());
    $image->save($file_path);

    // Check that the both the GD object and the Image object have an accurate     // record of the dimensions.     if (isset($expected['height']) && isset($expected['width'])) {

$this->logger->error("The image toolkit '@toolkit' failed loading image '@image'. Reported error: @class - @message", [
        '@toolkit' => $this->getPluginId(),
        '@image' => $this->getSource(),
        '@class' => get_class($t),
        '@message' => $t->getMessage(),
      ]);
      $this->preLoadInfo = NULL;
      return FALSE;
    }

    $this->setResource($resource);
    if (imageistruecolor($resource)) {
      return TRUE;
    }
    else {
      // Convert indexed images to truecolor, copying the image to a new       // truecolor resource, so that filters work correctly and don't result       // in unnecessary dither.       $data = [
        'width' => imagesx($resource),
        'height' => imagesy($resource),
        'extension' => image_type_to_extension($this->getType(), FALSE),
        'transparent_color' => $this->getTransparentColor(),

if ( ! $filename ) {
            $filename = $this->generate_filename( null, null, $extension );
        }

        if ( 'image/gif' === $mime_type ) {
            if ( ! $this->make_image( $filename, 'imagegif', array( $image, $filename ) ) ) {
                return new WP_Error( 'image_save_error', __( 'Image Editor Save Failed' ) );
            }
        } elseif ( 'image/png' === $mime_type ) {
            // Convert from full colors to index colors, like original PNG.             if ( function_exists( 'imageistruecolor' ) && ! imageistruecolor( $image ) ) {
                imagetruecolortopalette( $image, false, imagecolorstotal( $image ) );
            }

            if ( ! $this->make_image( $filename, 'imagepng', array( $image, $filename ) ) ) {
                return new WP_Error( 'image_save_error', __( 'Image Editor Save Failed' ) );
            }
        } elseif ( 'image/jpeg' === $mime_type ) {
            if ( ! $this->make_image( $filename, 'imagejpeg', array( $image, $filename, $this->get_quality() ) ) ) {
                return new WP_Error( 'image_save_error', __( 'Image Editor Save Failed' ) );
            }
        } elseif ( 'image/webp' == $mime_type ) {

public static function castStreamContext($stream, array $a, Stub $stub, bool $isNested)
    {
        return @stream_context_get_params($stream) ?: $a;
    }

    /** * @return array */
    public static function castGd($gd, array $a, Stub $stub, bool $isNested)
    {
        $a['size'] = imagesx($gd).'x'.imagesy($gd);
        $a['trueColor'] = imageistruecolor($gd);

        return $a;
    }

    /** * @return array */
    public static function castOpensslX509($h, array $a, Stub $stub, bool $isNested)
    {
        $stub->cut = -1;
        $info = openssl_x509_parse($h, false);