[Bug fix] Fix img2img processor with safety checker (#3127)

Fix img2img processor with safety checker

src/diffusers/pipelines/stable_diffusion/safety_checker.py

@@ -85,6 +85,9 @@ class StableDiffusionSafetyChecker(PreTrainedModel):
 
         for idx, has_nsfw_concept in enumerate(has_nsfw_concepts):
             if has_nsfw_concept:
+                if torch.is_tensor(images) or torch.is_tensor(images[0]):
+                    images[idx] = torch.zeros_like(images[idx])  # black image
+                else:
                     images[idx] = np.zeros(images[idx].shape)  # black image
 
         if any(has_nsfw_concepts):

tests/pipelines/stable_diffusion/test_stable_diffusion_img2img.py

@@ -453,6 +453,20 @@ class StableDiffusionImg2ImgPipelineSlowTests(unittest.TestCase):
 
         assert np.abs(image_slice.flatten() - expected_slice).max() < 5e-3
 
+    def test_img2img_safety_checker_works(self):
+        sd_pipe = StableDiffusionImg2ImgPipeline.from_pretrained("runwayml/stable-diffusion-v1-5")
+        sd_pipe.to(torch_device)
+        sd_pipe.set_progress_bar_config(disable=None)
+
+        inputs = self.get_inputs(torch_device)
+        inputs["num_inference_steps"] = 20
+        # make sure the safety checker is activated
+        inputs["prompt"] = "naked, sex, porn"
+        out = sd_pipe(**inputs)
+
+        assert out.nsfw_content_detected[0], f"Safety checker should work for prompt: {inputs['prompt']}"
+        assert np.abs(out.images[0]).sum() < 1e-5  # should be all zeros
+
 
 @nightly
 @require_torch_gpu