How can I develop a transformation that performs JPEG compression with a random QF?

vision
#1

I need a transform that performs JPEG compression to the image in question. The QF must be random and belong to a given subset.

#2

The imgaug library has a jpegcompression that takes a parameter on how much one wants to compress it. I’m guessing QF is quality factor?

#3

And how do I add it to my simple_transform?

# Transforms
    simple_transform = transforms.Compose(
        [
            transforms.ToTensor(),
            transforms.Normalize([0.485, 0.456, 0.406], [0.229, 0.224, 0.225])
        ]
    )

    # Dataset
    train_dataset = datasets.ImageFolder('data/train/', simple_transform)
    valid_dataset = datasets.ImageFolder('data/valid/', simple_transform)
#4

I’ve never done it but you could probably create a custom transform. Perhaps searching on google for pytorch lambda transform or whatever will help you find some working code of it

Edit: Did just that

def foo(x):
    return x / 255.0

transforms.Lambda(lambda x: foo(x))
#5

Perfect @Oli

def randomJPEGcompression(image):
    qf = random.randrange(10, 100)
    outputIoStream = BytesIO()
    image.save(outputIoStream, "JPEG", quality=qf, optimice=True)
    outputIoStream.seek(0)
    return Image.open(outputIoStream)

# Transforms
    simple_transform = transforms.Compose(
        [
            transforms.Lambda(randomJPEGcompression),
            transforms.ToTensor(),
            transforms.Normalize([0.485, 0.456, 0.406], [0.229, 0.224, 0.225])
        ]
    )
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