While converting a PIL image into a tensor why the pixels are changing?

Question

transform = transforms.Compose([transforms.ToPILImage(), transforms.ToTensor()])

Before applying the transformation

After applying the transformation

Q.1 Why the pixel values are changed?
Q.2 How to correct this?

Kauri

Answer 1

I was able to solve this problem by normalizing the input data before transforming it.
The problem was that ToPILImage() was discarding all the values which were greater than 1 hence the bright pixels became dark.

Kauri

Could you post the code here, please? That link is dead. – Gloria

Sorry for the VERY late reply, I wasn't active on SO for some time. Also unfortunately I don't have the code now, although iirc i just normalized the input image using transforms.Normalize @Gloria – Kauri

Answer 2

Q1: transforms.ToTensor() of torchvision normalizes your input image, i.e. puts it in the range [0,1] as it is a very common preprocessing step.

Q2: use torch.tensor(input_image) to convert image into a tensor instead.

Twentytwo

It doesn't work, and even if transforms.ToTensor() normalizes the input image the relative values of pixels should not change, but the bright pixels become completely dark when performing the transform. – Kauri