imagerotate - PHP code example

PHP Image Manipulation - How to Rotate, Crop and Replace Colors in Images

When you write php code that involves image manipulation, it is important to choose the right function. The standard GD library that comes with PHP is a powerful tool but it does not do everything you might need. There are a few specific functions that will allow you to rotate, crop and replace colors in your images.

Rotating an Image

If you want to rotate an image in PHP you should use the built in function imagerotate(). This function accepts four parameters: $image, $angle, $bgd_color and $ignore_transparent. The image is the image resource returned by one of the image creation functions such as imagecreatetruecolor(). The angle is the different rotation angle in degrees. The bgd_color is the background color of the uncovered zone after the rotation. The ignore_transparent is used to set if transparent colors are ignored or kept after the rotation. The function returns an image resource for the rotated image on success or FALSE if it fails.

Cropping and Replacing Colors

The best way to replace the colors in an image is with the GD library function imagecolorsforindex($image, $x, $y). This function takes a true color or RGB and gets or sets the pixel at the given index. This can be useful for a wide variety of images but it will vary in quality from image to image.

Another useful function in the GD library is imagecopyresized(). This function is more robust than imagerotate in that it allows you to resize an image with less loss of quality. However, this function will still leave "jaggies" visible if you resize an image with a lot of detail.

imagerotate example

// 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;
    }

    /** * Flattens transparencies * * @return $this */

try {
                // use in-memory stream to read the EXIF-metadata,                 // to avoid downloading the image twice from a remote filesystem                 fwrite($stream, $file);
                rewind($stream);

                $exif = @exif_read_data($stream);

                if ($exif !== false) {
                    if (!empty($exif['Orientation']) && $exif['Orientation'] === 8) {
                        $image = imagerotate($image, 90, 0);
                    } elseif (!empty($exif['Orientation']) && $exif['Orientation'] === 3) {
                        $image = imagerotate($image, 180, 0);
                    } elseif (!empty($exif['Orientation']) && $exif['Orientation'] === 6) {
                        $image = imagerotate($image, -90, 0);
                    }
                }
            } catch (\Exception) {
                // Ignore.             } finally {
                fclose($stream);
            }
        }

function _rotate_image_resource( $img, $angle ) {
    _deprecated_function( __FUNCTION__, '3.5.0', 'WP_Image_Editor::rotate()' );

    if ( function_exists( 'imagerotate' ) ) {
        $rotated = imagerotate( $img, $angle, 0 );

        if ( is_gd_image( $rotated ) ) {
            imagedestroy( $img );
            $img = $rotated;
        }
    }

    return $img;
}

/** * Flips an image resource. Internal use only. * * @since 2.9.0 * @deprecated 3.5.0 Use WP_Image_Editor::flip() * @see WP_Image_Editor::flip() * * @ignore * @param resource|GdImage $img Image resource or GdImage instance. * @param bool $horz Whether to flip horizontally. * @param bool $vert Whether to flip vertically. * @return resource|GdImage (maybe) flipped image resource or GdImage instance. */

  protected function execute(array $arguments) {
    // PHP installations using non-bundled GD do not have imagerotate.     if (!function_exists('imagerotate')) {
      $this->logger->notice('The image %file could not be rotated because the imagerotate() function is not available in this PHP installation.', ['%file' => $this->getToolkit()->getSource()]);
      return FALSE;
    }

    // Stores the original GD resource.     $original_res = $this->getToolkit()->getResource();

    if ($new_res = imagerotate($this->getToolkit()->getResource(), 360 - $arguments['degrees'], $arguments['background_idx'])) {
      $this->getToolkit()->setResource($new_res);
      imagedestroy($original_res);

      // GIFs need to reassign the transparent color after performing the       // rotate, but only do so, if the image already had transparency of its       // own, or the rotate added a transparent background.       if (!empty($arguments['gif_transparent_color'])) {
        $transparent_idx = imagecolorexactalpha($this->getToolkit()->getResource(), $arguments['gif_transparent_color']['red'], $arguments['gif_transparent_color']['green'], $arguments['gif_transparent_color']['blue'], $arguments['gif_transparent_color']['alpha']);
        imagecolortransparent($this->getToolkit()->getResource(), $transparent_idx);
      }

    public function rotate( $angle ) {
        if ( function_exists( 'imagerotate' ) ) {
            $transparency = imagecolorallocatealpha( $this->image, 255, 255, 255, 127 );
            $rotated      = imagerotate( $this->image, $angle, $transparency );

            if ( is_gd_image( $rotated ) ) {
                imagealphablending( $rotated, true );
                imagesavealpha( $rotated, true );
                imagedestroy( $this->image );
                $this->image = $rotated;
                $this->update_size();
                return true;
            }
        }