imagesavealpha - PHP code example

PHP Function ImagesaveAlpha

Managing images on your website can be time-consuming and error-prone, but with a little bit of PHP knowledge you can automate most image manipulation tasks. This article will introduce you to the GD library (short for Graphic Draw), which comes with PHP and handles almost all of your basic image manipulation needs.

GD supports most common image formats, including GIF, JPEG, PNG, TIFF and bmp. To get started working with image files, you must first make sure that GD is activated in your web server/host. You can check if it is by running ?php echo phpinfo();?>.

Most image manipulation functions in GD require a function name and one or more arguments. Arguments are like variables, but you must specify them after the function name and within parenthesis. The imagerotate() function, for example, requires a parameter that specifies the angle of rotation.

Aside from resizing, cropping and rotating images, GD has a number of other image processing functions. For example, the imagepng() function will create a PNG version of an image and can also be used to convert any other file type to a PNG. The imagecolorsforindex() function allows you to obtain the index of a particular color in an image.

You can also work with meta data stored in the headers of images by using the xexif functions. These can be accessed only if your PHP installation is compiled with the --enable-exif option.

imagesavealpha example

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. * } */

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 */

'@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(),
        ]);

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'],
            $thumbnailSize['height'],
            $originalImageSize['width'],
            $originalImageSize['height']
        );

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,
            $newSize['width'],
            $newSize['height'],
            $originalSize['width'],

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);
        }
        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);
        }

        $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. */

$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;
    }

    /** * Saves any changes that have been made to file. If no new filename is * provided, the existing image is overwritten, otherwise a copy of the * file is made at $target. * * Example: * $image->resize(100, 200, true) * ->save(); */