ALTRON image display: zooming, reading pixel values and tools

Is that bright spot on the part really saturated, or does it just look white on the monitor? You can't tell by eye. The ALTRON image display for area scan cameras doesn't just show the image; you can zoom in on any point and read the numeric pixel values.

Two displays, two uses

An area scan camera graph has two display nodes:

• Image Frame Viewer: The simple display. It shows each frame as it arrives. When you just want to see what the camera sees, this is enough.
• Advanced Image Frame Viewer: A more complete version that adds area zoom, point cursors and coordinate readout. Use this one for camera setup and troubleshooting.

Each display node in the graph creates a tab in the middle of the main window. Each tab's title also shows the name of the node that feeds data to that display. So if you have two displays at two points in the path, the tab titles tell you which is which.

Zooming and panning with the mouse

• The mouse wheel zooms.
• Right-click dragging pans the image.
• Double-clicking returns the view to its initial state.
• In the advanced display, dragging a box with the left button zooms into that area. This behaviour is controlled by Zoom on Area Selection, which is on by default.

In the simple display, zooming and panning are turned on with the Zoom / Pan option. None of this touches the recorded data; only the view changes.

Point cursors for reading values

When you want to watch several points at once, for example the black level in a corner and the brightness in the centre, use point cursors:

1. In the Advanced Image Frame Viewer settings, turn on Show Context Menu in the Point Cursor section. It is off by default.
2. Right-click on the image. Add cursor to pixel places a cursor on that pixel, and Add cursor at X,Y asks you for the exact column and row.
3. You can have up to 30 cursors, named P1, P2 and so on. Remove last cursor and Remove all cursors are in the same menu.

Three settings control how the values behave:

• Update Every (ms): Sets how often, in milliseconds, the values refresh. The range is 100 to 5000 and the default is 250. If you untick it, the values stay fixed.
• Neighbouring Size: Sets how many surrounding pixels are averaged. The range is 0 to 10 and the default is 2. Zero means the pixel alone. A larger number gives a steadier, less noisy reading.
• Precision: Number of decimal places, 0 to 4.

One thing people often ask us: the value under a cursor is calculated by the Average Mapper node. If you placed a cursor and no value appears next to it, check whether this node is in the graph.

Picking the colour of a point

In the Advanced Image Frame Viewer, the display's own diagnostics section always shows the coordinates of the pixel under the mouse. To pick a colour, click the point with the middle mouse button. Two values appear in the panel: the colour of the pixel itself and the average colour in a circle with a 50-pixel radius. You can copy either as three R G B numbers with Copy to Clipboard. This is very handy for comparing the colour of a part with a reference sample.

Tools in the View menu

• Image Probe: In the advanced display, if you hold Shift and drag with the left button, you draw a profile line. Holding Ctrl and dragging draws a region box. The Image Probe window in the View menu shows the data for that line or box.
• Live Histogram: Shows a live histogram of the image. It's the fastest way to see whether the brightness is hitting the ceiling.
• Full Camera View: Ctrl+F11 hides the side panels so the image fills the screen.

Both displays also have two more options: Rotate 90 Ccw rotates the image 90 degrees, in the view only. Date and Time writes the date and time on the image, and you can set its font size between 2 and 10.

Mistakes we see

• Judging saturation from the image colour instead of looking at the cursor value or the histogram.
• Setting Neighbouring Size to zero on a noisy image and then worrying about a value that keeps jumping up and down.
• Placing the display after gamma or a sharpener and expecting to see the raw sensor value. The display shows whatever data flows at the point where it is connected.

If you'd like to read more about the theory of pixels, this Wikipedia article (English) is a good start.

See the specifications of our area scan cameras on the area scan cameras page. If the values you read don't match what you expect, ask us through this page and we'll look for the cause together.