View - Zoom...

The View menu provides Zoom commands that duplicate the Zoom In, Zoom Out, and Zoom to Fit button commands on the main toolbar, plus a very useful Zoom to Native command.  



Zoom In - Zoom in one step.

Zoom Out - Zoom out one step.


Zoom to Native - Zoom so one pixel in an image is the size of one pixel on the monitor, or so one pixel is a whole number coordinate in drawings and labels.

Zoom to Fit - Zoom so the contents of the active layer fill the window.

Zoom to Native

The Zoom to Native command is used with images, with images from web servers, and with drawings and labels layers in maps.  When zooming to native scale in a map, the scale used is whatever is the native scale implied by the coordinate system metric in the coordinate system used by the map.


Images are popped open in Manifold zoomed to fit the size of a new, docked image window, given whatever is the size of the Manifold desktop and the space available next to any docked panes. That normally will involve some interpolation to put more or fewer image pixels into each pixel in the display screen, since it is not likely that the docked size of an image window will match the pixel dimensions of the image we open.


If we want to see the image in native scale, where one pixel in the image occupies one pixel on screen we choose View - Zoom to Native.  That command will automatically zoom the image in or out so that one pixel image is exactly one pixel on screen.

Web Servers

Web servers like the Bing image server provide tiles in a cascade of more detailed tiles as we zoom further into a display, up to some limiting, most detailed, level of tiles.  Beyond that most detailed level of tiles either pixels will be interpolated to be expanded, where a single pixel in a web served tile covers more and more pixels on screen, or the web server will issue blank tiles, perhaps with a "no data available" caption.  


Choosing Zoom to Native when a web server layer is the current layer will zoom to the most detailed tile level available, so the pixels in the tiles served by the web server will occupy exactly one pixel on screen.  That normally provides what looks like the best visual resolution.   Depending on the scene, we may get what seems to be a slightly more detailed view with a few mouse clicks of rotation in a wheel mouse to further zoom in, but that is only an apparent effect, as there is no more detailed data being sent, just the same data interpolated for what appear to be "fatter" pixels.

Drawings and Labels

Sometimes when creating objects in drawings, or labels in a labels component, for example, when using Manifold as a CAD editor or using Manifold to create diagrams for illustrations, we would like the coordinates we click for objects to be whole numbers, such as X,Y values of -165, 40 and not -165.4954783999, 40.9398312223.   


We can do that by first choosing View - Zoom to Native before we begin clicking to create objects.  That adjusts the scale in use so that each pixel on screen that can be clicked corresponds to a whole number coordinate value.   That works for either standalone drawing or label windows or for drawing or labels layers in a map window.

Example:  An Image at Native Scale

Illustrations in this documentation are often created using Manifold itself as a graphics editor.   Manifold makes it easy to combine raster and vectors in the same map window, so instead of using raster editors that have poor vector effects, or vector editors that do not well with rasters, occasionally it is easier to import an image into Manifold, add the image as a layer in a map, and then add vector effects in a drawing layer to compose the illustration desired.  



The illustration above shows how an image was created that appears in the Tables topic.  The green labeled table is an image that was imported from a .png format file and assigned the default Pseudo-Mercator projection. The Callout lines layer is a drawing that hosts the dotted green lines.   Vector visual effects such as dotted lines or labels are very easy in Manifold, but not so easy to do in some raster editors, so the dotted lines were added in a few seconds in Manifold.


However, for accurate image composition it is best to work at a scale where one pixel in the image is one pixel on screen.   The display seen above interpolates the image to fit into the window size that is available.  



We can Shift-click the title tab for the map to undock the window as seen above.   We have clicked the Zoom to Fit button to zoom the image to fit.  Because the image dimensions do not exactly match the size of the undocked window, again the pixels in the image are interpolated to fit the available size of the window.



Back in the Manifold desktop, we choose View - Zoom to Native.



The result is that the image is zoomed so that one pixel in the image appears in exactly one pixel on screen.  The resulting display is as sharp as the original use of pixels in Manifold.   We can now proceed to add layers and to do whatever edits we like, at the end making a screenshot to grab the composed image for further use in our editing workflow (future builds will add a Make Image tool, eliminating the need for making a screenshot).


 Zoom to Native is good, but it has to work around basic arithmetic and Manifold infrastructure designed to enable various coordinate systems. If a given display window size does not, for modulo arithmetic reasons, allow an exact 1:1 pixel zoom, sometimes after commanding Zoom to Native we might have to resize the undocked window a pixel or two to allow an exact 1:1 pixel match.  Since the system will on the fly adjust the display as we slightly resize the window, it is usually obvious and easy when we slightly resize the window and the display becomes razor sharp.


Why Pseudo-Mercator? -  Why was the .png imported and assigned Pseudo-Mercator?  When working with images or using Manifold for CAD-style editing, any projection that uses linear units of measure, such as meters, and which is centered on the 0,0 intersection of the Prime Meridian and the Equator is fine.  We may as well use Pseudo-Mercator.   A refinement for larger scale CAD drawings would be to use Mercator projection with a spherical Earth ellipsoid.


See Also









Web Servers


Status Bar - Scale