Contrast adjustments

Contrast adjustments

Slightly stretched image:
More stretched image

Figure 9.21: Open contrast adjustment dialog for primary or secondary image.

The images are initially assumed to span the entire 11-bit interval, from gray level 0 to gray level 2047. If you want to adjust the contrast, press Contrast..., then select primary or secondary image or use th equivalent contrast menu entries. A dialog will be displayed. For monochrome images, a dialog such as the one above is shown. For multispectral images, another dialog is shown. Both include min and max sliders. All gray levels below min will be set to black/minimum. All gray levels above max slider will be set to white/maximum. Values between min and max will be stretched linearly.

Because of the large span of gray levels, clicking and sliding with the mouse can be too inexact. To specify the min and max values more exactly, you can click on a slider and use the left and right arrow keys.

To see the result of your parameters, click the Apply button.

To close the dialog, click Close. The contrast dialog is "modeless", meaning that you do not have to close the dialog to continue the measurements.

Note, that contrast adjustments only influence the viewing of the image - the image data, and consequently the processes of Metria CityModeler on the image, are left untouched.

Your contrast settings are saved to your project file.

Contrast stretching and band selection of multispectral images

For multispectral images, you can choose which band to display in each of the red, green, and blue (RGB) channels by expanding the Band list box for each of the RGB channel. You can also stretch each RGB channel independently, by dragging its Min and Max sliders as described for grayscale contrast stretching. To drag all RGB Min or Max Sliders simultaneously, check the Apply on all bands check box.

Figure 9.22: Dialog for contrast stretching of multispectral images.