You have to change the code, because the conversion is made directly from the code.
In file function.php find this line
case('upload_logo'):
$package = Params::getFiles('logo');
if( $package['error'] == UPLOAD_ERR_OK ) {
if( move_uploaded_file($package['tmp_name'], WebThemes::newInstance()->getCurrentThemePath() . "images/logo.jpg" ) ) {
osc_add_flash_ok_message(__('The logo image has been uploaded correctly', 'modern'), 'admin');
} else {
osc_add_flash_error_message(__("An error has occurred, please try again", 'modern'), 'admin');
}
} else {
osc_add_flash_error_message(__("An error has occurred, please try again", 'modern'), 'admin');
}
header('Location: ' . osc_admin_render_theme_url('oc-content/themes/modern/admin/header.php')); exit;
break;
case('remove'):
if(file_exists( WebThemes::newInstance()->getCurrentThemePath() . "images/logo.jpg" ) ) {
@unlink( WebThemes::newInstance()->getCurrentThemePath() . "images/logo.jpg" );
osc_add_flash_ok_message(__('The logo image has been removed', 'modern'), 'admin');
} else {
osc_add_flash_error_message(__("Image not found", 'modern'), 'admin');
}
header('Location: ' . osc_admin_render_theme_url('oc-content/themes/modern/admin/header.php')); exit;
break;
And in this code which show the logo
if( !function_exists('logo_header') ) {
function logo_header() {
$html = '<img border="0" alt="' . osc_page_title() . '" src="' . osc_current_web_theme_url('images/logo.jpg') . '" />';
if( file_exists( WebThemes::newInstance()->getCurrentThemePath() . "images/logo.jpg" ) ) {
return $html;
} else if( osc_get_preference('default_logo', 'modern') && (file_exists( WebThemes::newInstance()->getCurrentThemePath() . "images/default-logo.jpg")) ) {
return '<img border="0" alt="' . osc_page_title() . '" src="' . osc_current_web_theme_url('images/default-logo.jpg') . '" />';
} else {
return osc_page_title();
}
}
}
Replace jpg with png