engine: add Renderer::colorSpace() interface

This is necessary for acquiring current format size.

@Issue: https://github.com/thorvg/thorvg/issues/976

src/lib/gl_engine/tvgGlRenderer.cpp

@@ -123,6 +123,12 @@ bool GlRenderer::endComposite(TVG_UNUSED Compositor* cmp)
 }
 
 
+ColorSpace GlRenderer::SwRenderer::colorSpace()
+{
+    return surface->cs;
+}
+
+
 bool GlRenderer::renderImage(TVG_UNUSED void* data)
 {
     //TODO: render requested images

src/lib/gl_engine/tvgGlRenderer.h

@@ -41,6 +41,7 @@ public:
     RenderRegion region(RenderData data) override;
     RenderRegion viewport() override;
     bool viewport(const RenderRegion& vp) override;
+    ColorSpace colorSpace() override;
 
     bool target(uint32_t* buffer, uint32_t stride, uint32_t w, uint32_t h);
     bool sync() override;

src/lib/sw_engine/tvgSwRenderer.cpp

@@ -664,6 +664,13 @@ bool SwRenderer::endComposite(Compositor* cmp)
 }
 
 
+ColorSpace SwRenderer::colorSpace()
+{
+    if (surface) return surface->cs;
+    else return ColorSpace::Unsupported;
+}
+
+
 bool SwRenderer::dispose(RenderData data)
 {
     auto task = static_cast<SwTask*>(data);

src/lib/sw_engine/tvgSwRenderer.h

@@ -47,6 +47,7 @@ public:
     RenderRegion region(RenderData data) override;
     RenderRegion viewport() override;
     bool viewport(const RenderRegion& vp) override;
+    ColorSpace colorSpace() override;
 
     bool clear() override;
     bool sync() override;

src/lib/tvgRender.h

@@ -221,6 +221,7 @@ public:
     virtual RenderRegion region(RenderData data) = 0;
     virtual RenderRegion viewport() = 0;
     virtual bool viewport(const RenderRegion& vp) = 0;
+    virtual ColorSpace colorSpace() = 0;
 
     virtual bool clear() = 0;
     virtual bool sync() = 0;