Compare Execution output images

You can easily compare images from multiple executions through the web application.

Web app

1. Open a project.
2. Select multiple executions using the checkbox in the Executions table.
3. Click Compare to open the metadata view with selected executions.
4. Click on the Images tab to open the image comparison view.

Image properties

The image comparison view is based on properties set for the output images. The properties can group related images together, define the comparison base and truth images to use for the group, and set the (optional) display name and default blend mode for individual images.

Example of comparison properties for an image datum:

{
  "vhic_group": "main group/secondary group/subgroup",
  "vhic_base": "name_of_the_comparison_base_file.png",
  "vhic_truth": "name_of_the_comparison_truth_file.png",
  "vhic_name": "Display name for this image",
  "vhic_blend": "multiply"
}

In this example, the image is part of the main group → secondary group → subgroup group hierarchy. The group uses name_of_the_comparison_base_file.png as the comparison base image, and name_of_the_comparison_truth_file.png as the comparison truth image.

The image is displayed with the name Display name for this image instead of the original filename. The image layer is blended using the multiply blend mode.

Grouping images

The vhic_group property is used to group related images together. The property is a string that can contain multiple levels of hierarchy separated by /.

Comparison base and truth images

The vhic_base and vhic_truth properties define the comparison base and truth images for the group. The base image is used as the reference image for comparison, and the truth image is used as the ground truth for comparison.

The base and truth images are required for building the comparison views – at least one image in a group must set them. The properties need to point to the same base and truth images for all images in the group (i.e. if image1.png has vhic_group: "group ABC", vhic_base: "base.png", and vhic_truth: "truth.png", then the other images in the group group ABC cannot have different values for vhic_base and vhic_truth).

Blend mode

There are currently four different blend modes available for comparing images:

• normal (default)
• multiply
• difference
• screen

You can scroll through the different blend modes in the UI: the property just sets the initial value used when the stack is built.

Image comparison stacks

You compare images by stacking them on top of each other as comparison layers. You can build as many custom stacks as you like by selecting the images you want to compare. There are four predefined stack views available:

• All images: All images from selected executions are displayed in their own stacks.
• Base + comparison: There is one stack for each image in the group (except for the base image). The base image is displayed as the first layer in each stack.
• Base + 1 comparison stack: There is one stack for each group. The base image is displayed as the first layer in each stack. Only one comparison stack is displayed at a time, with a quick switch widget to change the comparison stack.
• Side-by-side: There is one stack with the base and truth images, and one stack for the comparison images (on top of the base image). There is a side-by-side slider view to compare two of the comparison images, and a quick switch widget to change the displayed images.