Topics covered:
  • Labeling bounding boxes, polygons, bitmaps
  • Adding keypoints and attributes
  • Converting bounding boxes and polygons to bitmaps and vice-versa
  • Labeling occluded objects
  • Using smart labeling tool
  • Downloading and uploading image labels

You can download video tutorial here

Labeling tool tutorial transcription

Labeling images
To start labeling images, just right click on an image, and select labeling. By default, this will initiate labeling on all of the images. If you want to label only specific images, you can do so by using your mouse, or you can use the filtering options.
Creating and Labeling Bounding Boxes

To label bounding boxes, first click on the bounding box tool on the left hand menu, or click B on your keyboard. Then, simply draw a bounding box around the objects in the image that you would like to label. To enter the label name for an object, enter the text on the right hand side menu either by typing the name in manually, or by selecting it from the dropdown menu.

Once you have placed the bounding box on the image, you can resize or re-position the box as is necessary.

If you want to add a new bounding box on top of an existing bounding box, you can do so by clicking ‘New Object’ or N on your keyboard, and then draw the new bounding box. You can use a shortcut to change the label names of different bounding boxes by using the numbers on your keyboard. You are able to change which number corresponds to which label in the settings, to create shortcuts when labeling.

Keyboard shortcuts
We have many other keyboard shortcuts to assist labeling, which can be found by clicking on the blue question mark in the top right corner.
Creating and labeling polygons

To label polygons, switch to the polygon tool. Then, click on the image where you want to add points to the polygon. To finish the polygon, click on the original point of the polygon, or press enter on your keyboard. Once you have made your polygon, you can adjust the points of, or add new points to your polygon. To delete vertices on the polygon, either click on the delete button (on the right hand side) or click r, and then click on the vertex point. If you want to delete the whole polygon, you can do so by clicking on the middle of the polygon.

You can add holes to your polygon as well. To do so, click on the ‘New Hole’ feature (on the right hand side) or click H on your keyboard. Then, draw the hole inside the polygon. These holes can also be moved, resized or new points added.

Labeling occluded objects
Sometimes, one part of an object can be occluded by another object, leading to the same object appearing to be in two (or more) parts. If you would like to label these as one object, you can do so by first labeling the first polygon, and then clicking on the ‘New polygon in a group’ button, or by clicking G, and labeling the other polygon. In this case, one object will be labeled by two polygons. You can mark this label as being occluded by clicking on the button on the right hand side, or by clicking O on your keyboard. The objects marked as occluded will be made obvious by the dashed lines on the polygons.
Labeling key points and attributes

Another useful feature is the possibility to add key points to an object. Once you have drawn the bounding box, click on the ‘Add keypoints’ button on the right hand side, or click K on your keyboard. Then, click on the position where you want to add a keypoint and enter its name. Afterwards, you can add a few more keypoints and enter their names.

Once you have added the key points for that object, you can click on the save icon to save key point template. This will mean that for future objects of the same name, the key points labels will automatically appear in the same sequence as for the original object.

Additionally, you can add attributes for your labels. Click on the Attributes tool to add an attribute to the contents of the label. For example, if you were labelling human faces, you can add attributes such as Gender and Hair Colour to the labels.

It is possible to add keypoints and attributes to both bounding boxes and polygons.

Creating, labeling and converting Bitmaps

In addition to polygons, you can also label bitmaps. To draw bitmaps, click on the bitmaps tool on the left hand side. Then, draw a bitmap around your object in the image. You can resize the bitmap brush size on the right hand side menu. You can also use the Fill feature (G on your keyboard) and Erase feature (R on your keyboard) .

These bitmaps can be converted to polygons, and vice versa by clicking on the button on the right hand side menu. You can change the number of points that appear on the polygon once converted from the bitmap in the settings by checking or unchecking the “Simplify polygons converted from bitmap”. If this option is not ticked, it will increase the amount of points on the polygon.

Bounding boxes can also be converted into bitmaps, by clicking on the ‘Rasterize all objects’ option on the right hand side.

Smart Labeling Tool

In order to speed up the bitmap labeling process, you can use the smart labeling tool.

To use the smart labeling tool, first select the area that you want the tool to be active on the image. Then, click on the ‘foreground’ button on the right hand side, and quickly draw a bit of the foreground of the object. Once that is done, then click on the ‘background’ button, and quickly draw a bit of the background of the image. After this, you simply click on ‘Extract’ on the right hand side, and the smart labeling tool will automatically extract the object from the foreground that you draw. You can click on extract again and the result will change slightly. To improve the automatic extraction, you can use the foreground tool again to highlight more of the object in the image. Where the contract is high between the foreground and background, the smart labeling tool is very effective. Where the contrast difference is lower, the smart labeling tool is not as effective. In these instances, it is easiest to click ‘done’, and then zoom in and use the draw feature (E on your keyboard) to finish the bitmap manually.

Polylines and Points
The other labeling tools that we have are polylines and points.
Hiding or Showing Labels
In some cases, it will be useful to turn off the visibility of certain labels, so that you can label objects behind them as well. You can do this by clicking on the ‘eye’ icon on the right hand side menu relevant to each label. To either hide or show all labels in an image, click on either ‘hide all objects’ or ‘show all objects’.
Undoing changes
You can undo your last change by clicking on the undo button on the left hand side menu or by clicking on Ctrl + Z on your keyboard.
Downloading image labels

Once you are done labeling your image, you can download your image labels by clicking on the download button on the left hand side. Once you have clicked on the button, you can then choose which labels you want to download.

In the downloaded zip file; -you will find a json file with all of the image labels such as polygons, bounding boxes, polylines and points - classification labels in csv format -original images - the bitmaps, in two versions, both the coloured version which can be used for semantic segmentation or the black and white version which can be used for instance segmentation (it has a separate black and white bitmap for each object listed)

If you want to download labels for all images, you can do so by clicking the ‘Select all images’ button, then right click on any image, and then click on the download button. You will be presented with the same download options as before.

Uploading previously created image labels
Moreover, you can also upload image labels if you have previously labeled them elsewhere. Click on ‘Upload labels’ on the left hand menu, where you will be presented with the options to upload image labels as .csv , .json , colour bitmaps (.png) or B/W bitmaps (.zip)