RectLabel is an image-annotation tool to label images for bounding-box object detection.

Features

• Create a label dialog from JSON settings
• Layer order for overlapped boxes
• Zoom in on a point
• Quick zoom to existing boxes
• Draw a box including outside the image
• Smart guides for creating and transforming boxes
• Support the PASCAL VOC format

Note: While the software is classified as free, it offers in-App Purchases.