Normalize pixels to [0,1] using im2rec or reassign values to rec files

[lichen11]

I want to normalize the pixel values into [0, 255] without reading the images, normalizing them and re-saving them as jpeg. I used the im2rec API in R and notice there is no value normalization in this API. Then I tried reassign values to the rec files as follows:

val = mx.io.ImageRecordIter(
        path.imgrec = val_data,
        batch.size  = batch_size,
        data.shape  = data_shape,
        rand.crop   = FALSE,
        rand.mirror = FALSE)
val$reset()
val$iter.next()
val_data = val$value()$data
val_data = as.array(val_data)
val_data = val_data/255
val$value()$data = val_data

I got the error below
Error in val$value()$data = val_data :
invalid (NULL) left side of assignment

Is there another way to normalize the images by 255 in mxnet R? Thank you!

[leleamol]

@lichen11
For questions, please submit on MXNet discussion forum (https://discuss.mxnet.io), where it will get a wider audience and allow other to learn as well.
I'm closing this issue now in favor of the discussion forum issue you will file, please feel free to re-open if closed in error.
Thanks!

@mxnet-label-bot [R, Question]

[lichen11]

Hi, I actually also noticed an error in the MXNet R API im2rec. When the original images are actually normalized to [0,1], when using im2rec to pack the images, the pixel values are scaled to [0, 255].