Selection Settings Palette

Main Menu: View > Selection Palette 
Button:
in Tools Toolbar
Shortcut:
F6

This palette is related with the automatic area measurement tool, that measures areas within the same pixel range, both contiguously or across the image (This tool doesn't support Statistic Analysis or Histogram).

The Selection Settings palette automatically pop-ups when is clicked.

By clicking on any image pixel you will set the pixel reference value, unless you prefer to enter directly a Threshold value. The amount of tolerance will determine the selection size.

Tolerance:

The three sliders adjust the pixel tolerance for each color channel.

Tolerance lets you set how much deviation above and below the reference value should be included in the selection, therefore the selection pixel values range will be exactly double than the tolerance value.

You can use either RGB or HSL/HSV color modes to adjust the pixel tolerance or set a threshold and tolerance to select a pixel range. If you select RGB  (as the image below shows) or Threshold, you have the option of selecting Lock Channels, to use the same tolerance value for each channel. Setting different tolerance values for each channel is an alternative to be used when the selected pixels don't fit to the desired area.

Select HSL/HSV color models (shown in the image below) when the RGB color model doesn't allow selecting properly the desired area. HSL and HSV are grouped together because they have similar Hue and Saturation channels, in fact HSL and HSV are closely related colors models, so there is not much difference between them. Use the HSL and HSV in selection radio boxes below the Luminance slider to switch between HSL and HSV. if  you select HSV the Luminance slider will change its label to Value.

The Threshold option doesn't require clicking the image with the button, but selecting a threshold value and tolerance. It works in RGV/HSL or HSV modes.

Threshold  is used to select pixels in an image by specifying threshold and tolerance (or range) values. Each pixel is tested independently and it is either selected or not according to the same criteria, therefore selections cannot be limited to contiguous pixels.

In the example below threshold is 105 and tolerance 80, therefore all pixels with values between 25 and 185 in both three R, G and B channels will be selected.

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Only adjacent pixels within the tolerance range will be selected if Contiguous check box is selected, otherwise all image pixels within the tolerance range will be selected.

When measuring an area of contiguous pixels, regions connected only along a diagonal will not be included. Learn More.

If Invert is selected the current measurement area will be inverted. This feature is useful when the background is smoother than the objects we want to select., allowing us to select indirectly the objects by selecting the background that surrounds them.

The Only borders check box doesn't affects the measurement at all, but if selected, only the borders of all measurements will be drawn.

The Mask color box opens the color palette window, to modify the current area measurement color.

Grow / Shrink buttons

This two buttons expand or contract  an active selection by 1 pixel. The selection growths or shrinks in size while retaining its original shape.

Mode
Different selection modes can be set by clicking on any the six selection mode buttons or selecting the corresponding commands in the selection mode list box. You may specify whether to replace the current selection, create a new selection , add to an existing selection or subtract from a selection. Adding or subtracting can be done manually or automatically.

Mode

Action to perform when the image is clicked

The current area measurement will be replaced for a new one. Each time you click again, a new selection will be calculated and the previous one will disappear.

A new area measurement will be added to the image measurements.

The selected area will be added to the current area measurement.
This options only must be used when Contiguous is selected.

The selected area will be subtracted from the current area measurement.
This options only must be used when Contiguous is selected.

The automatic area selection tool will work like a pen, using the current pen brush size (set in the Tools Palette), allowing adding pixel to the selection by painting them manually.

The automatic area selection tool will work like an eraser, using the current pen brush size (set in the Tools Palette), allowing decreasing the selection by erasing parts of it manually.

  1. Each time the tolerance value for any channel is modified or when switching from RGB to HSL/HSV modes, the area measurement will be recalculated, and any selections added either manually or automatically will be lost.

  2. To create a new selection without modifying the previous one, select , click the image to create the selection and only then change the color or tolerance settings.

  3. To modify an area measurement, select it in the Measurement window datasheet, then you can modify its tolerance or color settings.