Add 2 nodes, remove alpha + convert image to grayscale

image_to_grayscale.py

@@ -0,0 +1,39 @@
+import torch
+
+class GrayscaleTransform:
+    @classmethod
+    def INPUT_TYPES(s):
+        return {
+            "required": {
+                "image": ("IMAGE",),
+                "preserve_alpha": ("BOOLEAN", {"default": False}),
+            },
+        }
+
+    RETURN_TYPES = ("IMAGE",)
+    FUNCTION = "transform_to_grayscale"
+
+    CATEGORY = "Bjornulf"
+
+    def transform_to_grayscale(self, image, preserve_alpha):
+        # Check if the image has an alpha channel
+        has_alpha = image.shape[3] == 4
+
+        # Extract RGB channels
+        rgb = image[:, :, :, :3]
+
+        # Convert to grayscale using the luminosity method
+        # Weights are based on human perception of color
+        grayscale = 0.2989 * rgb[:,:,:,0] + 0.5870 * rgb[:,:,:,1] + 0.1140 * rgb[:,:,:,2]
+        
+        # Expand dimensions to match original shape
+        grayscale = grayscale.unsqueeze(-1).repeat(1, 1, 1, 3)
+
+        if has_alpha and preserve_alpha:
+            # If the original image had an alpha channel and we want to preserve it
+            alpha = image[:, :, :, 3:4]
+            result = torch.cat([grayscale, alpha], dim=3)
+        else:
+            result = grayscale
+
+        return (result,)