ALTRON Virtual Camera: working without hardware using test image patterns
rahni
You don't have to wait for a camera to arrive to learn ALTRON. The virtual camera is a purely software camera that generates test image patterns and takes the exact place of a real camera in the graph. You can build and test the whole processing chain without a single physical camera.
The Virtual Camera Settings window for creating a virtual camera in ALTRON
We use it a lot ourselves: when we build a new graph, when we want to see how a plug-in behaves on predictable data, or when a customer's software team writes code before the hardware is delivered.
Creating a virtual camera
The creation window opens from the Tools menu with Manage Virtual Cameras. The same button also sits below the list of connected cameras. The form opens step by step; each step stays disabled until you complete the previous one:
Camera type: Choose Area scan or Line scan. A line scan camera delivers only one line at a time, so its height is always 1.
Pixel format: For an area scan camera, BW8, BW16 and Bayer are available. Colour in an area scan camera comes from the Bayer mosaic and is debayered in the graph. For a line scan camera, you have RGB8, RGB16 (48-bit colour), BW8 and BW16.
Pattern: Choose the image pattern; we describe them below.
Resolution: Enter the width and height, or press one of the three shortcuts 200×200, 640×480 and 1920×1080. Height only applies to an area scan camera.
Emit Rate: Sets the data generation rate. For an area scan camera it is in frames per second, and for a line scan camera in lines per second. The default is 25 frames per second for area scan and 1000 lines per second for line scan.
Add camera Press it. The camera appears next to the connected cameras with a new serial number starting with 0000V.
The Remove button deletes the selected camera. To delete all virtual cameras at once, press Remove All.
Eight image patterns and what each is for
1 Gaussian: A soft bright spot in the centre of the image; on a line scan camera, a bump in the middle of the line. It's good for seeing how plug-ins behave on a simple, symmetric shape.
2 Ramp: A linear ramp from zero at the left edge to the maximum value at the right edge, that is 255 at 8 bits and 65535 at 16 bits. Use this pattern to check levels, lookup tables and bit depth.
3 Color bar H and 4 Color bar V: Horizontal and vertical colour bars. They are only available with a colour format (RGB or Bayer) and are used to test the colour chain.
5 Static grad H and 6 Static grad V: Fixed horizontal and vertical gradients. On a line scan camera, the vertical gradient advances in the scan direction. Each time the number of lines reaches the image width, the pattern starts again.
7 White noise: Random white noise across the full value range, generated independently for each pixel. Use this pattern for load testing and for trying out noise filters.
8 Moving gradient: The default pattern: a gradient that keeps moving across the image so you can see frames updating.
There is also a ninth pattern, Spectrometer, which simulates an emission line spectrum. Because it has its own settings, we cover it in a separate article.
Common mistakes
Colour bars in a monochrome format: The Color bar patterns are disabled with BW8 and BW16. If the selected pattern doesn't match the format, Moving gradient is selected automatically. So if you see a moving image you didn't expect, check the format.
Emit Rate set too high: This value goes up to 2,000,000, and very high rates can fill the processing queue. Unless you're load testing, start with the default.
Changing settings after Add: This form sets up the cameras you add from now on. If you want to change a camera you've already created, remove it and add it again.
A practical tip
Combine the White noise pattern with a high Emit Rate and watch the Performance tab. Without any production line running, you can see which node in your graph falls behind under load. When the real camera arrives, you only swap the camera node and the rest of the work is ready. To get to know the software itself, see the ALTRON.
