imagealphablending - PHP code example

Using the PHP Function ImageAlphaBlending

PHP is a popular scripting language that is used to create dynamic web pages and can also be used to create images. The GD library, which is included with most installations of PHP, allows for the creation and editing of GIF, JPEG and PNG files. It is possible to use a variety of image-processing functions to set the colours ("colors" if you are using a different variant of English) of an image, write text to that image and draw lines in it.

The php function imagealphablending can be used to change the blending mode for an image. When drawing on a truecolor image, the alpha channel component of the color supplied to any drawing function such as imagesetpixel() determines how much of the existing color should be allowed to shine through. GD uses an alpha blending mode by default, but the php function allows you to disable it.

The php function imagecopyresized copies a rectangular area from one image to another, with the destination image and the src image identifier. The destination image and src image must have the same size, but the imagecopyresized function can stretch or shrink an image to fit the target area. This is a useful function for creating CAPTCHA images, or for designing banners and logos on the fly for use on a website.

imagealphablending example

if ( ! is_gd_image( $this->image ) ) {
            return new WP_Error( 'invalid_image', __( 'File is not an image.' ), $this->file );
        }

        $size = wp_getimagesize( $this->file );

        if ( ! $size ) {
            return new WP_Error( 'invalid_image', __( 'Could not read image size.' ), $this->file );
        }

        if ( function_exists( 'imagealphablending' ) && function_exists( 'imagesavealpha' ) ) {
            imagealphablending( $this->image, false );
            imagesavealpha( $this->image, true );
        }

        $this->update_size( $size[0], $size[1] );
        $this->mime_type = $size['mime'];

        return $this->set_quality();
    }

    /** * Sets or updates current image size. * * @since 3.5.0 * * @param int $width * @param int $height * @return true */

        $thumbnail = imagecreatetruecolor($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,
            0,
            0,
            $thumbnailSize['width'],

        $image = apply_filters( 'load_image_to_edit', $image, $attachment_id, $size );

        if ( function_exists( 'imagealphablending' ) && function_exists( 'imagesavealpha' ) ) {
            imagealphablending( $image, false );
            imagesavealpha( $image, true );
        }
    }

    return $image;
}

/** * Retrieves the path or URL of an attachment's attached file. * * If the attached file is not present on the local filesystem (usually due to replication plugins), * then the URL of the file is returned if `allow_url_fopen` is supported. * * @since 3.4.0 * @access private * * @param int $attachment_id Attachment ID. * @param string|int[] $size Optional. Image size. Accepts any registered image size name, or an array * of width and height values in pixels (in that order). Default 'full'. * @return string|false File path or URL on success, false on failure. */

$create = 'imagecreatetruecolor';
            $copy   = 'imagecopyresampled';
        } else {
            $create = 'imagecreate';
            $copy   = 'imagecopyresized';
        }

        $dest = $create($this->width, $this->height);

        // for png and webp we can actually preserve transparency         if (in_array($this->image()->imageType, $this->supportTransparency, true)) {
            imagealphablending($dest, false);
            imagesavealpha($dest, true);
        }

        $copy($dest, $src, 0, 0, (int) $this->xAxis, (int) $this->yAxis, $this->width, $this->height, $origWidth, $origHeight);

        imagedestroy($src);
        $this->resource = $dest;

        return $this;
    }

function wp_imagecreatetruecolor( $width, $height ) {
    $img = imagecreatetruecolor( $width, $height );

    if ( is_gd_image( $img )
        && function_exists( 'imagealphablending' ) && function_exists( 'imagesavealpha' )
    ) {
        imagealphablending( $img, false );
        imagesavealpha( $img, true );
    }

    return $img;
}

/** * Based on a supplied width/height example, returns the biggest possible dimensions based on the max width/height. * * @since 2.9.0 * * @see wp_constrain_dimensions() * * @param int $example_width The width of an example embed. * @param int $example_height The height of an example embed. * @param int $max_width The maximum allowed width. * @param int $max_height The maximum allowed height. * @return int[] { * An array of maximum width and height values. * * @type int $0 The maximum width in pixels. * @type int $1 The maximum height in pixels. * } */

// 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,
            0,
            0,
            0,
            0,

'@toolkit' => $this->getPluginId(),
          '@image' => $destination,
          '@class' => get_class($t),
          '@message' => $t->getMessage(),
        ]);
        $success = FALSE;
      }
    }
    else {
      // Image types that support alpha need to be saved accordingly.       if (in_array($this->getType(), [IMAGETYPE_PNG, IMAGETYPE_WEBP], TRUE)) {
        imagealphablending($this->getResource(), FALSE);
        imagesavealpha($this->getResource(), TRUE);
      }
      try {
        $success = $function($this->getResource(), $destination);
      }
      catch (\Throwable $t) {
        $this->logger->error("The image toolkit '@toolkit' failed saving image '@image'. Reported error: @class - @message", [
          '@toolkit' => $this->getPluginId(),
          '@image' => $destination,
          '@class' => get_class($t),
          '@message' => $t->getMessage(),
        ]);

    $original_res = $this->getToolkit()->getResource();

    // Create the resource.     if (!$res = imagecreatetruecolor($arguments['width'], $arguments['height'])) {
      return FALSE;
    }

    // Fill the resource with transparency as possible.     switch ($type) {
      case IMAGETYPE_PNG:
      case IMAGETYPE_WEBP:
        imagealphablending($res, FALSE);
        $transparency = imagecolorallocatealpha($res, 0, 0, 0, 127);
        imagefill($res, 0, 0, $transparency);
        imagealphablending($res, TRUE);
        imagesavealpha($res, TRUE);
        break;

      case IMAGETYPE_GIF:
        if (empty($arguments['transparent_color'])) {
          // No transparency color specified, fill white transparent.           $fill_color = imagecolorallocatealpha($res, 255, 255, 255, 127);
        }