save texture to file as a PNG image

Change-Id: I5605b80f95d89599efe58cf65e1ce3f3581d401f

vcl/inc/opengl/texture.hxx

@@ -23,7 +23,7 @@
 #include <GL/glew.h>
 #include <vcl/dllapi.h>
 #include <vcl/salgtype.hxx>
-
+#include <rtl/ustring.hxx>
 #include <tools/gen.hxx>
 
 class ImplOpenGLTexture
@@ -71,6 +71,8 @@ public:
     void            Unbind();
     void            Read( GLenum nFormat, GLenum nType, sal_uInt8* pData );
 
+    void            SaveToFile(const OUString& rFileName);
+
     GLenum          GetFilter() const;
     void            SetFilter( GLenum nFilter );
 

vcl/opengl/texture.cxx

@@ -23,7 +23,8 @@
 
 #include "svdata.hxx"
 
-#include "vcl/salbtype.hxx"
+#include <vcl/salbtype.hxx>
+#include <vcl/pngwrite.hxx>
 
 #include "opengl/framebuffer.hxx"
 #include "opengl/texture.hxx"
@@ -262,6 +263,26 @@ void OpenGLTexture::Unbind()
     CHECK_GL_ERROR();
 }
 
+void OpenGLTexture::SaveToFile(const OUString& rFileName)
+{
+    std::vector<sal_uInt8> pBuffer(GetWidth() * GetHeight() * 4);
+    Read(GL_BGRA, GL_UNSIGNED_BYTE, pBuffer.data());
+    BitmapEx aBitmap = OpenGLHelper::ConvertBGRABufferToBitmapEx(pBuffer.data(), GetWidth(), GetHeight());
+    try
+    {
+        vcl::PNGWriter aWriter(aBitmap);
+        SvFileStream sOutput(rFileName, StreamMode::WRITE);
+        aWriter.Write(sOutput);
+        sOutput.Close();
+    }
+    catch (...)
+    {
+        SAL_WARN("vcl.opengl", "Error writing png to " << rFileName);
+    }
+
+    CHECK_GL_ERROR();
+}
+
 void OpenGLTexture::Read( GLenum nFormat, GLenum nType, sal_uInt8* pData )
 {
     if( mpImpl == NULL )