Difference between revisions of "Background Image"
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==Import ESRI geo-referenced image in MOHID GIS== | ==Import ESRI geo-referenced image in MOHID GIS== | ||
| − | + | ===Automatic Method=== | |
ESRI geo-referenced images are comprised of two files: the image (e.g. image.jpg) and the "world file" with the coordinates (e.g. image.jpgw): | ESRI geo-referenced images are comprised of two files: the image (e.g. image.jpg) and the "world file" with the coordinates (e.g. image.jpgw): | ||
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| − | '''Note:''' If loading the file fails and all that you see is a white image (but in the right place) the problem is the picture resolution is too high for Mohid Gis to load it. | + | '''Note:''' If loading the file fails and all that you see is a white image (but in the right place) the problem is the picture resolution is too high for Mohid Gis to load it. Reduce its resolution by 50% and change the jpgw doubling pixel/unit distance X and pixel/unit distance X. |
| − | |||
| − | Alternatively | + | ===Manual Method=== |
| + | Alternatively you can convert by hand the world file to Mohid GIS img file, | ||
* WIDTH (HEIGHT) = number of width (height) pixels time pixels/unit distance X (Y). The pixel information of the image can be seen in [http://www.gimp.org/ GIMP], for example. | * WIDTH (HEIGHT) = number of width (height) pixels time pixels/unit distance X (Y). The pixel information of the image can be seen in [http://www.gimp.org/ GIMP], for example. | ||
* The Y coordinate must be decreased by ''height pixels times pixels/unit distance Y'' to go from Upper Left Corner (ESRI) to Lower Left Corner (Mohid GIS) | * The Y coordinate must be decreased by ''height pixels times pixels/unit distance Y'' to go from Upper Left Corner (ESRI) to Lower Left Corner (Mohid GIS) | ||
* Write the path to the file in IMAGE_FILE | * Write the path to the file in IMAGE_FILE | ||
* open the .img file created in MOHID GIS as a background image (file type). | * open the .img file created in MOHID GIS as a background image (file type). | ||
Latest revision as of 20:34, 13 August 2009
Contents
What it is
A background image data item consists of an image and its geo-reference, given in the *.img file:
IMAGE_FILE : C:\temp\389_.jpg --> Path to the image file X : 0 --> Coordinate X of the Lower Left Corner Y : 0 --> Coordinate Y of the Lower Left Corner WIDTH : 16008 --> Width in distance units HEIGHT : 10011 --> Height in distance units MIP_MAPPED : 1 MAINTAIN_RATIO : 1 ALPHA_VALUE : 1
Import ESRI geo-referenced image in MOHID GIS
Automatic Method
ESRI geo-referenced images are comprised of two files: the image (e.g. image.jpg) and the "world file" with the coordinates (e.g. image.jpgw):
3 --> pixels/unit distance X 0.000000000000 0.000000000000 -3 --> pixels/unit distance Y -111989.9 --> Coordinate X of Upper Left Corner -70266.15 --> Coordinate Y of Upper Left Corner
This are the actions to import geo-referenced images to MOHID GIS
- Add New Item.
- Background Image; choose file name.
- In this new layer created, if a window does not appear automatically, go to Properties (F4, or right-click, or Menu Data Items/Properties).
- Choose the image file (browse)
- Click "Import ArcView GeoRef" to import automatically the "world file"
- Data Items -> Save All, in order to save the just created .img file
Now, everytime you want to open that background image go to Open->Background Image (type of file) and select the .img file created.
Note: If loading the file fails and all that you see is a white image (but in the right place) the problem is the picture resolution is too high for Mohid Gis to load it. Reduce its resolution by 50% and change the jpgw doubling pixel/unit distance X and pixel/unit distance X.
Manual Method
Alternatively you can convert by hand the world file to Mohid GIS img file,
- WIDTH (HEIGHT) = number of width (height) pixels time pixels/unit distance X (Y). The pixel information of the image can be seen in GIMP, for example.
- The Y coordinate must be decreased by height pixels times pixels/unit distance Y to go from Upper Left Corner (ESRI) to Lower Left Corner (Mohid GIS)
- Write the path to the file in IMAGE_FILE
- open the .img file created in MOHID GIS as a background image (file type).
