Add img alt text to imagegraph(); resolves #420. (#422)

- Update ExtractImageLinksRDD to grab alt text
- Add alt_text column to imagegraph
- Update tests

src/main/scala/io/archivesunleashed/matchbox/ExtractImageLinksRDD.scala

@@ -27,20 +27,22 @@ object ExtractImageLinksRDD {
     *
     * @param src the src link
     * @param html the content from which links are to be extracted
-    * @return a sequence of image links.
+    * @return a sequence of (source, image link, alt-text).
     */
-  def apply(src: String, html: String): Seq[String] = {
+  def apply(src: String, html: String): Seq[(String, String, String)] = {
     if (html.isEmpty) Nil
     try {
-      val output = mutable.MutableList[String]()
+      val output = mutable.MutableList[(String, String, String)]()
       val doc = Jsoup.parse(html)
       val links: Elements = doc.select("img[src]")
+      val alt: Elements = doc.select("img[alt]")
       val it = links.iterator()
       while (it.hasNext) {
         val link = it.next()
         link.setBaseUri(src)
         val target = link.attr("abs:src")
-        output += (target)
+        val altText = link.attr("alt")
+        output += ((src, target, altText))
       }
       output
     } catch {

src/main/scala/io/archivesunleashed/package.scala

@@ -381,18 +381,16 @@ package object archivesunleashed {
     def imagegraph(): DataFrame = {
       val records = rdd
         .keepValidPages()
-        .flatMap(r => ({
-          val src = r.getUrl
-          val imageUrls = ExtractImageLinksRDD(src, r.getContentString)
-          imageUrls.map(url => (src, url))
-        })
-          .map(t => (r.getCrawlDate, t._1, t._2)))
-        .map(t => Row(t._1, t._2, t._3))
+        .flatMap(r => ExtractImageLinksRDD(r.getUrl, r.getContentString)
+          .map(t => (r.getCrawlDate, t._1, t._2, t._3)))
+        .filter(t => t._2 != "" && t._3 != "")
+        .map(t => Row(t._1, t._2, t._3, t._4))
 
       val schema = new StructType()
         .add(StructField("crawl_date", StringType, true))
         .add(StructField("src", StringType, true))
         .add(StructField("image_url", StringType, true))
+        .add(StructField("alt_text", StringType, true))
 
       val sqlContext = SparkSession.builder();
       sqlContext.getOrCreate().createDataFrame(records, schema)

src/test/scala/io/archivesunleashed/matchbox/ExtractImageLinksTest.scala

@@ -25,26 +25,31 @@ import org.scalatest.junit.JUnitRunner
 @RunWith(classOf[JUnitRunner])
 class ExtractImageLinksRDDTest extends FunSuite {
   test("Extract simple image links RDD") {
-    val fragment =
-      """Image here: <img src="http://foo.bar.com/pic.png"> and another <img src="http://baz.org/a/b/banner.jpg"/>"""
-    val extracted = ExtractImageLinksRDD("", fragment).toList
+    val fragment: String =
+      """Image here: <img src="http://foo.bar.com/pic.png" alt="picture"> and another <img src="http://baz.org/a/b/banner.jpg" alt="baz banner"/>"""
+    val extracted: Seq[(String, String, String)] = ExtractImageLinksRDD("", fragment)
     assert(extracted.size == 2)
-    assert("http://foo.bar.com/pic.png" == extracted(0))
-    assert("http://baz.org/a/b/banner.jpg" == extracted(1))
+    assert("http://foo.bar.com/pic.png" == extracted(0)._2)
+    assert("picture" == extracted(0)._3)
+    assert("http://baz.org/a/b/banner.jpg" == extracted(1)._2)
+    assert("baz banner" == extracted(1)._3)
   }
 
   test("Extract relative image links RDD") {
-    val fragment =
-      """Image here: <img src="pic.png"> and another <img src="http://baz.org/a/b/banner.jpg"/> and <img src="../logo.gif"/>"""
-    val extracted = ExtractImageLinksRDD("http://foo.bar.com/a/page.html", fragment)
+    val fragment: String =
+      """Image here: <img src="pic.png" alt="picture"> and another <img src="http://baz.org/a/b/banner.jpg" alt="baz banner" /> and <img src="../logo.gif" alt="LOGO" />"""
+    val extracted: Seq[(String, String, String)] = ExtractImageLinksRDD("http://foo.bar.com/a/page.html", fragment)
     assert(extracted.size == 3)
-    assert("http://foo.bar.com/a/pic.png" == extracted(0))
-    assert("http://baz.org/a/b/banner.jpg" == extracted(1))
-    assert("http://foo.bar.com/logo.gif" == extracted(2))
+    assert("http://foo.bar.com/a/pic.png" == extracted(0)._2)
+    assert("picture" == extracted(0)._3)
+    assert("http://baz.org/a/b/banner.jpg" == extracted(1)._2)
+    assert("baz banner" == extracted(1)._3)
+    assert("http://foo.bar.com/logo.gif" == extracted(2)._2)
+    assert("LOGO" == extracted(2)._3)
   }
 
   test("Test image link errors RDD") {
-    val fragment =
+    val fragment: String =
       """Image here: <img src="pic.png"> and another <img src="http://baz.org/a/b/banner.jpg"/> and <img src="../logo.gif"/>"""
     assert(ExtractImageLinksRDD("", "") == Nil)
     // Need way of creating an exception here