Different ways to fix the HTTP image upload errors in WordPress

.htaccess

SetEnv MAGICK_THREAD_LIMIT 1

functions.php

<?php

    add_filter( 'wp_image_editors', 'image_editor_gd_default' );
    function image_editor_gd_default( $editors ) {

        $gd_editor = 'WP_Image_Editor_GD';
        $editors = array_diff( $editors, array( $gd_editor ) );

        array_unshift( $editors, $gd_editor );
        return $editors;
    }

?>

wp-config.php

define( 'WP_MEMORY_LIMIT', '256M' );