Raster Properties Dialog:Symbology

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2009年9月9日 (水) 00:38時点におけるSanak (トーク | 投稿記録)による版

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Symbology Tab

QGIS can render raster layers in two different ways :

  • Single band - one band of the image will be rendered as gray or in pseudocolors.
  • Three band color - three bands from the image will be rendered, each band representing the red, green or blue component that will be used to create a color image.

Within both render types you can invert the color output using the CheckBox.pngInvert color map checkbox.

Single Band Rendering

This selection offers you two possibilites to choose. At first you can select which band you like to use for rendering (if the dataset has more than one band).

The second option offers a selection of available colortables for rendering.

The following settings are available through the dropdownbox color map Grayscale SelectString.png, where grayscale is the default setting. Also available are

  • Pseudocolor
  • Freak Out
  • Colormap

When selecting the entry color map Colormap SelectString.png, the tab Colormap becomes available. See more on that at chapter 6.3.3.

QGIS can restrict the data displayed to only show cells whose values are within a given number of standard deviations of the mean for the layer. This is useful when you have one or two cells with abnormally high values in a raster grid that are having a negative impact on the rendering of the raster. This option is only available for pseudocolor images.

Three band color

This selection offers you a wide range of options to modify the appereance of your rasterlayer. For example you could switch color-bands from the standard RGB-order to something else.

Also scaling of colors are available.


Tip 23 VIEWING A SINGLE BAND OF A MULTIBAND RASTER


If you want to view a single band (for example Red) of a multiband image, you might think you would set the Green and Blue bands to “Not Set”. But this is not the correct way. To display the Red band, set the image type to grayscale, then select Red as the band to use for Gray.