From 955eef83b0181b57f367f15fefccc63bddf3da86 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Mon, 19 Apr 2021 23:47:29 +0200
Subject: [PATCH] LibWeb: Add basic support for HTMLCanvasElement.toDataURL()
 :^)

This allows you to serialize a <canvas> element's bitmap into a
data: URI. Pretty neat! :^)
---
 Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.cpp | 12 ++++++++++++
 Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.h   |  2 ++
 Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.idl |  2 ++
 3 files changed, 16 insertions(+)

diff --git a/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.cpp
index fed960276e0..b1e505f25b0 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.cpp
@@ -24,8 +24,10 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <AK/Base64.h>
 #include <AK/Checked.h>
 #include <LibGfx/Bitmap.h>
+#include <LibGfx/PNGWriter.h>
 #include <LibWeb/CSS/StyleResolver.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/HTML/CanvasRenderingContext2D.h>
@@ -102,4 +104,14 @@ bool HTMLCanvasElement::create_bitmap()
     return m_bitmap;
 }
 
+String HTMLCanvasElement::to_data_url(const String& type, [[maybe_unused]] Optional<double> quality) const
+{
+    if (!m_bitmap)
+        return {};
+    if (type != "image/png")
+        return {};
+    auto encoded_bitmap = Gfx::PNGWriter::encode(*m_bitmap);
+    return URL::create_with_data(type, encode_base64(encoded_bitmap), true).to_string();
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.h b/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.h
index 43df33f7107..257500220fb 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.h
@@ -48,6 +48,8 @@ public:
     unsigned width() const;
     unsigned height() const;
 
+    String to_data_url(const String& type, Optional<double> quality) const;
+
 private:
     virtual RefPtr<Layout::Node> create_layout_node() override;
 
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.idl b/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.idl
index 5a04895fb46..6fc0a0ba4a8 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.idl
+++ b/Userland/Libraries/LibWeb/HTML/HTMLCanvasElement.idl
@@ -4,4 +4,6 @@ interface HTMLCanvasElement : HTMLElement {
     readonly attribute unsigned long width;
     readonly attribute unsigned long height;
 
+    USVString toDataURL(optional DOMString type = "image/png", optional double quality);
+
 };