resolves #382 set alt value

README.md

@@ -269,6 +269,7 @@ Here's a list of all attributes used in the built-in HTML 5 converter:
 - `float`
 - `align`
 - `role`
+- `title` (used to define an alternative text description of the diagram)
 
 **Options**
 

ruby/lib/asciidoctor/extensions/asciidoctor_kroki/extension.rb

@@ -148,8 +148,6 @@ def process(processor, parent, attrs, diagram_type, diagram_text, logger)
         if (subs = attrs['subs'])
           diagram_text = parent.apply_subs(diagram_text, parent.resolve_subs(subs))
         end
-        title = attrs.delete('title')
-        caption = attrs.delete('caption')
         attrs.delete('opts')
         format = get_format(doc, attrs, diagram_type)
         attrs['role'] = get_role(format, attrs['role'])
@@ -162,11 +160,14 @@ def process(processor, parent, attrs, diagram_type, diagram_text, logger)
                                          source_location: doc.reader.cursor_at_mark,
                                          http_client: KrokiHttpClient
                                        }, logger)
+        alt = get_alt(attrs)
+        title = attrs.delete('title')
+        caption = attrs.delete('caption')
         if TEXT_FORMATS.include?(format)
           text_content = kroki_client.text_content(kroki_diagram)
           block = processor.create_block(parent, 'literal', text_content, attrs)
         else
-          attrs['alt'] = get_alt(attrs)
+          attrs['alt'] = alt
           attrs['target'] = create_image_src(doc, kroki_diagram, kroki_client)
           block = processor.create_image_block(parent, attrs)
         end

ruby/spec/asciidoctor_kroki_spec.rb

@@ -18,6 +18,21 @@
 <div class="content">
 <img src="https://kroki.io/plantuml/svg/eNpLzMlMTlXQtVNIyk-yUshIzcnJBwA9iwZL" alt="Diagram">
 </div>
+</div>)
+    end
+    it 'should use the title attribute as the alt value' do
+      input = <<~'ADOC'
+        [plantuml,title="Alice saying hello to Bob"]
+        ....
+        alice -> bob: hello
+        ....
+      ADOC
+      output = Asciidoctor.convert(input, standalone: false)
+      (expect output).to eql %(<div class="imageblock kroki">
+<div class="content">
+<img src="https://kroki.io/plantuml/svg/eNpLzMlMTlXQtVNIyk-yUshIzcnJBwA9iwZL" alt="Alice saying hello to Bob">
+</div>
+<div class="title">Figure 1. Alice saying hello to Bob</div>
 </div>)
     end
     it 'should use png if kroki-default-format is set to png' do