[Bug] Save gt images in PGGAN's forward (#1328)

* save gt image to data samples in forward

* add ut to ensure gt img is saved

mmedit/models/editors/pggan/pggan.py

@@ -175,6 +175,8 @@ def forward(self,
             gen_sample = EditDataSample()
             if data_samples:
                 gen_sample.update(data_samples[idx])
+            if isinstance(inputs, dict) and 'img' in inputs:
+                gen_sample.gt_img = PixelData(data=inputs['img'][idx])
             if isinstance(outputs, dict):
                 gen_sample.ema = EditDataSample(
                     fake_img=PixelData(data=outputs['ema'][idx]),

tests/test_models/test_editors/test_pggan/test_pggan.py

@@ -72,6 +72,10 @@ def test_pggan_cpu(self):
                 assert np.isclose(pggan._actual_nkimgs[-1], 0.012, atol=1e-8)
 
         # test forward
+        outputs = pggan.forward(dict(img=torch.randn(3, 3, 16, 16)))
+        assert len(outputs) == 3
+        assert all(['gt_img' in out for out in outputs])
+
         outputs = pggan.forward(dict(num_batches=2))
         assert len(outputs) == 2
         assert all([out.fake_img.data.shape == (3, 16, 16) for out in outputs])