Raster Eigenschappen Dialoog¶

Laag Info¶

The General menu displays basic information about the selected raster, including the layer source path, the display name in the legend (which can be modified) and the number of columns, rows and No-Data Values of the raster.

Coördinaten referentie systeem¶

Ook het Coordinaten Referentie Systeem (CRS) wordt hier weergegeven als een PROJ.4-tekst. Deze kan worden aangepast via de knop [Opgeven...].

Schaalafhankelijke zichtbaarheid¶

Daarnaast kunnen schaalafhankelijke zichtbaarheden worden ingesteld in dit tabblad. Vink daarvoor het aanvinkvak schaalafhankelijke zichtbaarheid aan en stel het bereik van de schalen waarvoor de data getoond moet worden op de kaart.

Onderin kun je een ‘thumbnail’, een kleine afbeelding van de laag zien, het gebruikte legenda symbool en het kleurenpalet.

Enkelbands Renderen¶

QGIS offers four different Render types. The renderer chosen is dependent on the data type.

1. Multiband color - if the file comes as a multi band with several bands (e.g. used with a satellite image with several bands)
2. Paletted - if a single band file comes with an indexed palette (e.g. used with a digital topographic map)
3. Singleband gray- (one band of) the image will be rendered as gray, QGIS will choose this renderer if the file neither has multi bands, nor has an indexed palette nor has a continous palette (e.g. used with a shaded relief map)
4. Singleband pseudocolor - this renderer is possible for files with a continuous palette, e.g. the file has got a color map (e.g. used with an elevation map)

Multibands kleur

Met de multibands kleur renderer zullen drie banden van het image worden gebruikt om te renderen, waarbij elke band staat voor de rode, groene of blauwe component die worden gebruikt om een kleurenafbeelding op te bouwen. Je kunt kiezen tussen verschillende Contrast verbeterings methoden: ‘Geen verbetering’, ‘Stretch to MinMax’, ‘Stretch and clip to MinMax’ en ‘Clip to min max’.

Figure Raster 2:

Raster Renderer - Multibands kleur

This selection offers you a wide range of options to modify the appearance of your rasterlayer. First of all you have to get the data range from your image. This can be done by choosing the Extent and pressing [Load]. QGIS can Estimate (faster) the Min and Max values of the bands or use the Actual (slower) Accuracy.

Now you can scale the colors with the help of the Load min/max values section. A lot of images have few very low and high data. These outliers can be eliminated using the Cumulative count cut setting. The standard data range is set from 2% until 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 the whole data included in the original image. E.g. QGIS creates a color table with 256 values, given the fact that you have 8bit bands. You can also calculate your color table using the Mean +/- standard deviation x . Then only the values within the standard deviation or within multiple standard deviations are considered for the color table. 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.

Alle berekeningen kunnen ook worden gedaan voor de Huidige extent.

Paletted

This is the standard render option for singleband files that already include a color table, where each pixel value is assigned to a certain color. In that case, the palette is rendered automatically. If you want to change colors assigned to certain values, just double-click on the color and the Select color dialog appears.

Figure Raster 3:

Raster Renderer - Paletted

Contrastverhoging

Enkelbands grijs

This renderer allows you to render a single band layer with a Color gradient ‘Black to white’ or ‘White to black’. You can define a Min and a Max value with choosing the Extend first and then pressing [Load]. QGIS can Estimate (faster) the Min and Max values of the bands or use the Actual (slower) Accuracy.

Figure Raster 4:

Raster Renderer - Enkelbands grijs

With the Load min/max values section scaling of the color table is possible. Outliers can be eliminated using the Cumulative count cut setting. The standard data range is set from 2% until 98% of the data values and can be adapted manually. With this setting the gray character of the image can disappear. Further settings can be made with Min/max and Mean +/- standard deviation x . While the first one creates a color table with the whole data included in the original image the second creates a colortable that only considers values within the standard deviation or within multiple standard deviations. 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.

Enkelbands pseudokleur

This is a render option for single band files including a continous palette. You can also create individual color maps for the single bands here.

Figure Raster 5:

Raster Renderer - Enkelbands pseudokleur

Er zijn drie manieren van kleurinterpolatie beschikbaar:

1. Discreet

2. Lineair

3. Exact

In de linkerblok voegt de knop ^{Handmatig waarden toevoegen} een waarde toe aan een kleurentabel. De knop ^{Geselecteerde regel verwijderen} verwijderd een waarde van een kleurentabel en de knop ^{Sorteer onderdelen kleurenkaart} sorteert de kleurentabel op basis van de pixelwaarde gegeven in de kolom Waarde. Door te dubbelklikken op de kolom Waarde kun je ook een specifieke waarde toevoegen. Door te dubbelklikken op de kolom Kleur opent de dialoog Select Color waarin je een kleur kunt kiezen die van toepassing is op gegeven waarde.. Daarnaast kun je ook elke kleur een Label geven maar deze waarde zal niet getoond worden wanneer de tool Objecten Identificeren wordt gebruikt. Je kunt de knop ^{Laad kleurenkaart van band} gebruiken waarmee de kleurentabel van de band probeert de laden (indien aanwezig). Je kunt ook de knoppen ^{Laden kleurenkaart van bestand} of ^{Exporteer kleurenkaart naar bestand} gebruiken om een bestaande kleurentabel te laden of om deze te bewaren voor een andere sessies.

In the right block Generate new color map allows you to create newly categorized colormaps. For the Classification mode ‘Equal interval’ you only need to select the number of classes and press the button Classify. You can invert the colors of the the color map by clicking the Invert checkbox. In case of the Mode ‘Continous’ QGIS creates classes depending on the Min and Max automatically. Defining Min/Max values can be done with the help of Load min/max values section. A lot of images have few very low and high data. These outliers can be eliminated using the Cumulative count cut setting. The standard data range is set from 2% until 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 the whole data included in the original image. E.g. QGIS creates a color table with 256 values, given the fact that you have 8bit bands. You can also calculate your color table using the Mean +/- standard deviation x . Then only the values within the standard deviation or within multiple standard deviations are considered for the color table.

Het renderen van kleuren¶

For every Band rendering a Color rendering is possible.

You can achieve special rendering effects for your raster file(s) using one one of the blending modes (see blend_modes).

Further settings can be made in modifiying the Brightness, the Saturation and the Contrast. You can 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 modiy the ‘Strength’.

Resampling¶

The Resampling option makes it appearance when you zoom in and out of the image. Resampling modes can optimize the appearance of the map. They calculate a new gray value matrix through a geometric transformation.

While 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. Sharp features are caused to be blurred now. The effect is a smoother image. The method can be applied e.g. to digital topographic raster maps.