I have image files with read-only attribute set in source folder. I need to copy them to destination folder in most cases several times in gulpfile.js.
You can use gulp-chmod to handle permissions on your files.
So if you want to set your images readable and writable for everybody, you could go with something like:
var chmod = require('gulp-chmod');
gulp.task('copy-images', function() {
gulp.src(path_resource_images + '**/*.jpg')
.pipe(chmod(666))
.pipe(gulp.dest(path_app_images));
});