Raster histogram
From AWF-Wiki
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# After clicking {{button|text=Open}} , the raster layer appears on the QGIS canvas. | # After clicking {{button|text=Open}} , the raster layer appears on the QGIS canvas. | ||
# Right click the layer name in the Layers panel and select {{mitem|text=Properties --> Histogram}} | # Right click the layer name in the Layers panel and select {{mitem|text=Properties --> Histogram}} | ||
| − | + | # Click {{button|text=Compute Histogram}}. A histogram for all bands is displayed (Figure '''A'''). Left click and drag a box on the diagram to zoom in. [[File: Qgis_histogram_multiband.png|thumb|left|200px|'''Figure A:''' Line histograms of all bands]] | |
| − | Click | + | |
| − | [[File: Qgis_histogram_multiband.png|thumb|left|200px|'''Figure A:''' Line histograms of all bands]] | + | |
Click on {{button|text=Pref/Actions}} and deactivate ''Draw as lines''. Activate ''Show selected band'' and ''Always show min/max markers''. | Click on {{button|text=Pref/Actions}} and deactivate ''Draw as lines''. Activate ''Show selected band'' and ''Always show min/max markers''. | ||
The value range of the selected band data is evenly divided into bins. The histogram shows how many pixels of the image fall into each of the bins (Figure '''B''')[[File: Qgis_histogram_singleband.png|thumb|right|200px|'''Figure B:''' Histogram of a single selected band]]. Click on [[File: Qgis_save_icon.png|20px]]. The graphics may be saved as png file. | The value range of the selected band data is evenly divided into bins. The histogram shows how many pixels of the image fall into each of the bins (Figure '''B''')[[File: Qgis_histogram_singleband.png|thumb|right|200px|'''Figure B:''' Histogram of a single selected band]]. Click on [[File: Qgis_save_icon.png|20px]]. The graphics may be saved as png file. | ||
Revision as of 18:28, 21 October 2018
Using Layer Properties
- Click Click the Open Data Source Manger
and then Add raster layer 
and select the file /geodata/raster/s2/Subset_S2A_MSIL2A_20170619T_MUL.tif.
- After clicking Open , the raster layer appears on the QGIS canvas.
- Right click the layer name in the Layers panel and select Properties --> Histogram
- Click Compute Histogram. A histogram for all bands is displayed (Figure A). Left click and drag a box on the diagram to zoom in.
Figure A: Line histograms of all bands
Click on Pref/Actions and deactivate Draw as lines. Activate Show selected band and Always show min/max markers.
The value range of the selected band data is evenly divided into bins. The histogram shows how many pixels of the image fall into each of the bins (Figure B)
. The graphics may be saved as png file.
Using R scripts
- If the processing toolbox is not visible, select Processing --> Toolbox.
- In the processing toolbar, type Get R scripts into the search field and click to open it. In the Install scripts and model windows unfold the folder Not installed and activate Advanced histogram as shown below in the screenshot. Click OK.
.
- In the processing toolbar, type Get R scripts into the search field and click to open the diaolog window. Specify the Input raster Layer and click the button ... on to select the path and filename for the output graphics file. Click Run.
.
Be patient and have a look on the messages in the log window as some additional R packages need to be downloaded. The resulting graphics shows all histograms side by side.
