How to not copy images translated to base64 in gulp?

Question

gulp.js

Today is the first day since I started to deal with the assembly of projects using Gulp, so do not kick much.
Using gulp-css-base64 , images smaller than 50Kb are converted to base64 in css.
How can I make sure that the image files processed in this way are not copied to the folder with the built project, but remain only in src?
My gulpfile.js

'use strict';

var gulp = require('gulp'),
    watch = require('gulp-watch'),
    rigger = require('gulp-rigger'),
    cssBase64 = require('gulp-css-base64');

var path = {
    build: {
        html: 'build/',
        js: 'build/js/',
        css: 'build/css/',
        img: 'build/img/',
        fonts: 'build/fonts/'
    },
    src: {
        html: 'src/*.html',
        js: 'src/js/*.js',
        style: 'src/css/*.css',
        img: 'src/img/**/*.*',
        fonts: 'src/fonts/**/*.*'
    },
    watch: {
        html: 'src/**/*.html',
        js: 'src/js/**/*.js',
        style: 'src/css/**/*.css',
        img: 'src/img/**/*.*',
        fonts: 'src/fonts/**/*.*'
    },
    clean: './build'
};

gulp.task('clean', function (cb) {
    rimraf(path.clean, cb);
});

gulp.task('html:build', function () {
    gulp.src(path.src.html)
        .pipe(rigger())
        .pipe(gulp.dest(path.build.html));
});

gulp.task('js:build', function () {
    gulp.src(path.src.js)
        .pipe(rigger())
        .pipe(gulp.dest(path.build.js));
});

gulp.task('style:build', function () {
    gulp.src(path.src.style)

        .pipe(cssBase64({
            maxWeightResource: 5000, //Размер файла в bytes
            extensionsAllowed: ['.gif', '.jpg', '.png']
        }))

        .pipe(gulp.dest(path.build.css));
});

gulp.task('image:build', function () {
    gulp.src(path.src.img)
        .pipe(gulp.dest(path.build.img));
});

gulp.task('fonts:build', function() {
    gulp.src(path.src.fonts)
        .pipe(gulp.dest(path.build.fonts))
});

gulp.task('build', [
    'html:build',
    'js:build',
    'style:build',
    'fonts:build',
    'image:build'
]);

gulp.task('watch', function(){
    watch([path.watch.html], function(event, cb) {
        gulp.start('html:build');
    });
    watch([path.watch.style], function(event, cb) {
        gulp.start('style:build');
    });
    watch([path.watch.js], function(event, cb) {
        gulp.start('js:build');
    });
    watch([path.watch.img], function(event, cb) {
        gulp.start('image:build');
    });
    watch([path.watch.fonts], function(event, cb) {
        gulp.start('fonts:build');
    });
});

gulp.task('default', ['build', 'watch']);