imagecreatefromstring - PHP code example

PHP Functions For Image Manipulation

Image manipulation is a common task in web development, and PHP has many built-in functions that make it easy to do. These are often used in conjunction with the GD library, which is included with most PHP installations. With a little bit of knowledge about the GD library and how it works, you can use a variety of built-in image manipulation functions to save time and avoid errors.

For example, the imagecreatefromstring function allows you to create an image from a string. This can be useful if you want to create a thumbnail for a larger image that is too large. To do this, you would pass in the string that you want to create an image of and the destination file that you want to save it to. The function will then create a new physical image of the desired size. Then it will either resample the image to create the thumbnail or simply copy the image to the destination.

You can also use the imagerotate() function to rotate an image. However, you have to be careful with this one because it can cause the image to lose quality. The reason is because the rotation can leave a gap or an uncovered area on the image. The imagecreatefromstring function can help to avoid this problem by creating an image that is the same width as the original image.

Another very useful function is the imagecolorat(). This function allows you to get or set the color of any pixel in an image. This is particularly useful if you need to replace an image's background or fill in gaps in an image with solid colors. However, this function requires that the image is a true-color image. For a grayscale image, you will have to use other methods such as masking and bitshifting.

imagecreatefromstring example

->setParameter('{{ width }}', $width)
                ->setParameter('{{ height }}', $height)
                ->setCode(Image::PORTRAIT_NOT_ALLOWED_ERROR)
                ->addViolation();
        }

        if ($constraint->detectCorrupted) {
            if (!\function_exists('imagecreatefromstring')) {
                throw new LogicException('Corrupted images detection requires installed and enabled GD extension.');
            }

            $resource = @imagecreatefromstring(file_get_contents($value));

            if (false === $resource) {
                $this->context->buildViolation($constraint->corruptedMessage)
                    ->setCode(Image::CORRUPTED_IMAGE_ERROR)
                    ->addViolation();

                return;
            }

            imagedestroy($resource);
        }
    }

/** * Determines the extension of the file according to * the given path and calls the right creation * method for the image extension * * @throws RuntimeException * * @return resource */
    private function createImageResource(string $fileContent, string $imagePath)
    {
        $image = imagecreatefromstring($fileContent);
        if ($image === false) {
            throw new RuntimeException(sprintf('Image is not in a recognized format (%s)', $imagePath));
        }

        return $image;
    }

    /** * Returns the extension of the file with passed path */
    private function getImageExtension(string $path): string
    {

if ( ! $file_contents ) {
            return new WP_Error( 'error_loading_image', __( 'File does not exist?' ), $this->file );
        }

        // WebP may not work with imagecreatefromstring().         if (
            function_exists( 'imagecreatefromwebp' ) &&
            ( 'image/webp' === wp_get_image_mime( $this->file ) )
        ) {
            $this->image = @imagecreatefromwebp( $this->file );
        } else {
            $this->image = @imagecreatefromstring( $file_contents );
        }

        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 );
        }

$this->process($cmd);
    }

    /** * Return the width of an image. * * @return int */
    public function _getWidth()
    {
        return imagesx(imagecreatefromstring(file_get_contents($this->resource)));
    }

    /** * Return the height of an image. * * @return int */
    public function _getHeight()
    {
        return imagesy(imagecreatefromstring(file_get_contents($this->resource)));
    }

if ( ! is_file( $file ) ) {
        /* translators: %s: File name. */
        return sprintf( __( 'File “%s” does not exist?' ), $file );
    }

    if ( ! function_exists('imagecreatefromstring') )
        return __('The GD image library is not installed.');

    // Set artificially high because GD uses uncompressed images in memory.     wp_raise_memory_limit( 'image' );

    $image = imagecreatefromstring( file_get_contents( $file ) );

    if ( ! is_gd_image( $image ) ) {
        /* translators: %s: File name. */
        return sprintf( __( 'File “%s” is not an image.' ), $file );
    }

    return $image;
}

/** * Scale down an image to fit a particular size and save a new copy of the image. * * The PNG transparency will be preserved using the function, as well as the * image type. If the file going in is PNG, then the resized image is going to * be PNG. The only supported image types are PNG, GIF, and JPEG. * * Some functionality requires API to exist, so some PHP version may lose out * support. This is not the fault of WordPress (where functionality is * downgraded, not actual defects), but of your PHP version. * * @since 2.5.0 * @deprecated 3.5.0 Use wp_get_image_editor() * @see wp_get_image_editor() * * @param string $file Image file path. * @param int $max_w Maximum width to resize to. * @param int $max_h Maximum height to resize to. * @param bool $crop Optional. Whether to crop image or resize. Default false. * @param string $suffix Optional. File suffix. Default null. * @param string $dest_path Optional. New image file path. Default null. * @param int $jpeg_quality Optional. Image quality percentage. Default 90. * @return mixed WP_Error on failure. String with new destination path. */

/** @var MediaFolderEntity $folder */
        $folder = $this->mediaFolderRepository->search($criteria, $context)->get($mediaFolderId);
        $media->setMediaFolder($folder);
    }

    private function getImageResource(MediaEntity $media): \GdImage
    {
        $filePath = $this->urlGenerator->getRelativeMediaUrl($media);
        /** @var string $file */
        $file = $this->getFileSystem($media)->read($filePath);
        $image = @imagecreatefromstring($file);
        if ($image === false) {
            throw MediaException::thumbnailNotSupported($media->getId());
        }

        if (\function_exists('exif_read_data')) {
            /** @var resource $stream */
            $stream = fopen('php://memory', 'r+b');

            try {
                // use in-memory stream to read the EXIF-metadata,                 // to avoid downloading the image twice from a remote filesystem