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QGIS User Guide, Release 2.2
can be done with the help of the Load min/max values section. A lot of images have a few very low and high data.
Cumulative count cut setting. The standard data range is set from
These outliers can be eliminated using the
2% to 98% of the data values and can be adapted manually. With this setting, the gray character of the image can
disappear. With the scaling option
Min/max, QGIS creates a color table with all of the data included in the
original image (e.g., QGIS creates a color table with 256 values, given the fact that you have 8 bit bands). You can
Mean +/- standard deviation x
. Then, only the values within
also calculate your color table using the
the standard deviation or within multiple standard deviations are considered for the color table.
Renderização Cor
For every Band rendering, a Color rendering is possible.
You can also achieve special rendering effects for your raster file(s) using one of the blending modes (see Janela
das Propriedades da Camada Vectorial).
Further settings can be made in modifiying the Brightness, the Saturation and the Contrast. You can also use a
Grayscale option, where you can choose between ‘By lightness’, ‘By luminosity’ and ‘By average’. For one hue
in the color table, you can modify the ‘Strength’.
Reamostragem
The Resampling option makes its appearance when you zoom in and out of an image. Resampling modes can
optimize the appearance of the map. They calculate a new gray value matrix through a geometric transformation.
Figura 13.6: Renderização Raster - Reamostragem
When applying the ‘Nearest neighbour’ method, the map can have a pixelated structure when zooming in. This
appearance can be improved by using the ‘Bilinear’ or ‘Cubic’ method, which cause sharp features to be blurred.
The effect is a smoother image. This method can be applied, for instance, to digital topographic raster maps.
13.2.3 Menu Transparência
QGIS has the ability to display each raster layer at a different transparency level. Use the transparency slider
to indicate to what extent the underlying layers (if any) should be visible though the current
raster layer. This is very useful if you like to overlay more than one raster layer (e.g., a shaded relief map overlayed
by a classified raster map). This will make the look of the map more three dimensional.
Additionally, you can enter a raster value that should be treated as NODATA in the Additional no data value menu.
Uma forma ainda mais flexível para personalizar a transparência pode ser feito no: guilabel: seção de opções de
transparência personalizado. A transparência de cada pixel pode ser definido aqui.
13.2. Janela de Propriedades do Projecto
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