Render page as a base64 string.

Provided API for the Webpage object:
- renderBase64PNG()
- renderBase64JPG()
- renderBase64BMP()

Addresses [Issue #547](http://code.google.com/p/phantomjs/issues/detail?id=547).

src/webpage.cpp

@@ -46,6 +46,7 @@
 #include <QWebPage>
 #include <QWebInspector>
 #include <QMapIterator>
+#include <QBuffer>
 #include <QDebug>
 
 #include "networkaccessmanager.h"
@@ -546,6 +547,36 @@ bool WebPage::render(const QString &fileName)
     return buffer.save(fileName);
 }
 
+QString WebPage::renderBase64PNG()
+{
+    return renderBase64("PNG");
+}
+
+QString WebPage::renderBase64JPG()
+{
+    return renderBase64("JPG");
+}
+
+QString WebPage::renderBase64BMP()
+{
+    return renderBase64("BMP");
+}
+
+QString WebPage::renderBase64(const char *format)
+{
+    QImage rawPageRendering = renderImage();
+
+    // Prepare buffer for writing
+    QByteArray bytes;
+    QBuffer buffer(&bytes);
+    buffer.open(QIODevice::WriteOnly);
+
+    // Writing image to the buffer, using PNG encoding
+    rawPageRendering.save(&buffer, format);
+
+    return bytes.toBase64();
+}
+
 QImage WebPage::renderImage()
 {
     QSize contentsSize = m_mainFrame->contentsSize();
@@ -593,7 +624,6 @@ QImage WebPage::renderImage()
     }
 
     m_webPage->setViewportSize(viewportSize);
-
     return buffer;
 }
 

src/webpage.h

@@ -108,6 +108,9 @@ public slots:
 
     QVariant evaluateJavaScript(const QString &code);
     bool render(const QString &fileName);
+    QString renderBase64PNG();
+    QString renderBase64JPG();
+    QString renderBase64BMP();
     bool injectJs(const QString &jsFilePath);
     void _appendScriptElement(const QString &scriptUrl);
     QObject *_getGenericCallback();
@@ -132,6 +135,7 @@ private slots:
 
 private:
     QImage renderImage();
+    QString renderBase64(const char *format = "PNG");
     bool renderPdf(const QString &fileName);
     void applySettings(const QVariantMap &defaultSettings);
     QString userAgent() const;