|MapGazer – Using Images|
An image is a mark that displays an image on a map; the image has a specific location and size, so it can be used to display geographical information – such as satellite or drone images or a cave survey – onto a map, or you can add an image that simply illustrates features not visible on a map. Images are drawn ‘beneath’ other marks so they do not obscure them.
To create an image, you can:
Either of these will open the file-selector to choose an image to display. The image is then shown on the map, with a border; you can then left-click on any edge or corner of the border and drag it to adjust the image position and size. If you left-click on the image itself you can drag it to change its position without affecting its size.
You can hide the border of an image by right-clicking on the image or its border and clicking Hide image border. To show it again, right-click on the image (or where the border was) and again click Hide image border.
The size of the image in pels (image pixels) and the coordinates of its SW and NE corners will be shown at top-left of the map when the cursor is over, or dragging, the border or content of the image (you can turn these off using the Settings → Status display → Show image coordinates menu item).
The position or geographical size of an image is not affected by zooming, so you can zoom in to position it accurately. You can also open one or more extra windows (press ‘v’) and then use those windows to zoom in on different edges of the image.
When loaded, an image has a fixed aspect ratio. You can adjust its aspect ratio if necessary by unselecting Fixed aspect ratio in the pop-up menu or in the Properties dialog (see below) and then either drag the border of the image that you wish to change or enter a numerical aspect ratio in the Properties dialog and click Apply.
Similarly, an image has an image effect that is used when it is displayed. This may be none (the image is displayed as-is) or it may be graphic (white or near-white areas of the image are excluded from the image and are transparent, and transparency of the remainder depends on brightness). The graphic effect is useful for showing images like drawings or cave surveys – see the screenshots below. The image effect can be changed from the pop-up menu or in the Properties dialog (see below). The image effect may also be auto, which means that MapGazer will attempt to determine which effect to use automatically.
To change the properties (name, border colour, aspect ratio, image effect, link URL, etc.) of an image, right-click on the image border or content and select the Properties menu item; for more details, see Mark properties. You can change the displayed width of the image border using Settings → Line widths.
At any time you can view the image’s coordinates, and copy details to the clipboard for use by another application, by right-clicking on the image border or content and choosing the Details menu item.
To change the format used for Latitude and Longitude, select Settings → Position formats on the menu bar; see the General settings page for details.
To move between images (if you have more than one image displayed), either
In either case the order used is the chronological order in which the images were loaded or created.
Images can be saved to or loaded from GPX files:
To save an image right-click on the image or its border and select Save image to GPX file on the pop-up menu (this includes its position and properties, including border colour and aspect ratio). Alternatively, all marks (including all images) can be saved using the Marks → Save marks to GPX file menu item (or press the ‘s’ key).
To load a GPX file, use the Marks → Load marks from GPX file menu item (or press the ‘L’ key). This will open a dialog which you can use to select the GPX file to open. Any marks (tracks, routes, waypoints, images, and areas) in the file will then immediately be shown on the map (you may have to zoom or change the map, or move it, for the marks to be in view).
Depending on the source of the GPX file, image borders may have a default (grey) colour or may have a colour that was set later.
If an image has been loaded from a GPX file it can be adjusted as described above. At any time you can reset an image loaded from a GPX file to its original data by right-clicking on the image border and selecting Reset image.
To delete an image, right-click on the image or its border and select Delete image on the pop-up menu.
|MapGazer and these web pages were written by Mike Cowlishaw; Please send me any corrections, suggestions, etc.|
All content © Mike Cowlishaw, 2014–2017,
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This page was last updated on 2017-12-03 by mfc.