Image augmentation

Requirements

Requires the image-dataset-converter-imgaug library.

Download the 17 flowers object detection VOC XML dataset and extract it.

Plugins

Convert VOC XML to YOLO (crop/rotate)

The following converts VOC XML annotations into YOLO ones. It also augments the dataset with randomly adding cropped/rotated images to the stream (-m add), with the annotations getting processed accordingly:

idc-convert \
  -l INFO \
  from-voc-od \
    -l INFO \
    -i "./voc/*.xml" \
  crop \
    -m add \
    -f 0.1 \
    -t 0.2 \
    -u \
  rotate \
    -m add \
    -f "-45" \
    -t 45 \
  to-yolo-od \
    -l INFO \
    -o ./yolo-split-augmented \
    --labels ./yolo-split-augmented/labels.txt \
    --split_names train val test \
    --split_ratios 70 15 15

Here is an example of a processed image (image_0001.jpg):

Convert VOC XML to MS COCO (resize)

The following converts VOC XML annotations into smaller MS COCO ones, using a maximum width of 300 while keeping the aspect ratio intact. The data also gets split into train/validation/test:

idc-convert \
  -l INFO \
  from-voc-od \
    -l INFO \
    -i "./voc/*.xml" \
  resize \
    -W 300 \
    -H keep-aspect-ratio \
  to-coco-od \
    -l INFO \
    -o ./coco-split-small \
    --split_names train val test \
    --split_ratios 70 15 15

Split images into smaller ones

With the sub-images filter it is possible to split images into smaller ones or extract just specific regions of interest from images. The idc-generate-regions tool can be used to generate regions for a set number of rows/columns or fixed row heights/column widths.

For images that are at maximum 800x800, we can generate regions for a 2x2 grid as follows:

idc-generate-regions \
  -l INFO \
  -W 800 \
  -H 800 \
  -r 2 \
  -c 2

Will output this, with each quadruplet consisting of x, y, width and height:

0,0,400,400 400,0,400,400 0,400,400,400 400,400,400,400

These regions we can now use with the sub-images filter to generate smaller images:

idc-convert \
  -l INFO \
  from-voc-od \
    -l INFO \
    -i "./voc/*.xml" \
  sub-images \
    -l INFO \
    -r 0,0,400,400 400,0,400,400 0,400,400,400 400,400,400,400 \
    -p \
    -e \
  to-yolo-od \
    -l INFO \
    -o ./yolo-sub \
    --labels ./yolo-sub/labels.txt

Using -p we will keep partial annotations, ones that got cut off a bit, and with -e we will suppress images that have no annotations in them.

Using the meta-sub-images filter, you can feed the small images that were generated through the specified base filter. The output of this filter gets reassembled and forwarded. This base filter can be a simple filter or a more complex pipeline, which passes the images through a Redis model, for instance.