I have an image I use as overlay in a vector layer in my openlayer web application. The idea is the same as showed in this example
What I do not understand is how to set a valid resolution to my image so that every time the user changes the zoom of the map, the image width and height is adjusted to cover its real geographical area.
In the example above some images are used and placed at some specific locations using a specific and hard-coded resolution factor.
Assume I have an image 400x400 pixel which represents an area of 400x400 kilometers, I need to recalculate the width and height of my image every time the zoom factor changes using a formula like this:
imageWidth = imageWidthInPixel * theResolution / map.getResolution();
imageHeight = imageHeightInPixel * theResolution / map.getResolution();
where 'theResolution' is the value I need to calculate some way I don't know. I guess this is a value that depends on the area expressed in kilometers or meters the image covers, but I am not able to find out a relation that has a sense. As explained above, in the example I reported, these values are hard-coded and depends on the image but there is no way to understand how these values are calculated.
Please help me understand this.
If you know the projection of your image, it would be easiest to simply define the image as a layer defined in OpenLayers with the appropriate projection. At that point, OpenLayers will handle the zooming and panning for you.
Related
My actual Image is
Here I need to resize the image 140*80(Width*height)
But after resize the circle in the image becomes oval how to prevent that.
Your current image resolution is 700*312 has a ratio of 1:2.2435897435897435897435897435897..
The resolution you are trying to get is 140*80 has a ratio of 1:1.75.
In order to get a perfect circle, you must maintain the same ratio between the images.
If acceptable, try resizing your image to 140*62.4 (62.4 = 140/(700/312)).
More info about Aspect Ratio on Wikipedia .
Specifically for Xamarin, please show us what components are you using, or some example code so answers could be more specific.
I've seen a few libraries that pixelate images, some of them even feature non-square shapes such as The Pixelator's circle and diamond shapes.
I'm looking however to make a particular shape, I want a "pixel" that is 19x27 px. Essentially, the image would still look pixelated but it would use tallish rectangle shapes as the pixel base.
Are there any libraries out there that do this, if not, what alterations to existing algorithms/functions would I need to make to accomplish this?
Unless I am not understanding your question, the algorithm you need is quite simple!
Just break your image up into a grid of rectangles the size you want (in this case 19x27). Loop over each section of the grid and take the average color of the pixels inside (you can simply take the average of each channel in RGB independently). Then set all of the pixels contained inside to the average color.
This would give you an image that is the same size as your input. You could of course resize your image first to a more appropriate output size.
You might want to look up convolution matrices.
In a shader, you would use your current pixel location to grab a set of nearby pixels from the original image to render to a pixel in a new buffer image.
It is actually just a slight variation of the Box Blur image processing algorithm except that instead of grabbing from the nearby pixels you would grab by the divisions of the original image relative to the 19x27 divisions of the resulting image.
I have an image of 780x585. I am resizing this image to 1246.93x935.19 with scaleMode=ScaleMode.LETTERBOX.
When the user clicks on a graphic and drags it into the picture, I am supposed to get the pixel position where the graphic was dropped.
I do that by listening to the mouse up event and by calling getPixel with the (x,y) coordinates coming from the event when the mouse click is released.
Strange thing is that I get the value of the pixel but not the real one. Instead, I get the value corresponding to the image with it's normal size without being resized.
Does anyone have a clue why this is happening?
Thanks,
Dave
When applying some visual changes to a component (like moving, rotating or stretching as in here), Flex will be applying a transormation matrix to modify only the visual appearance of the object.
Let's say you're moving an image by doing image.width *= 2; the actual image width will be modified. If you do image.matrix.scale(2, 1); (this is pseudo-code), the visual appearance will be modified so you can see the resizing but the the actual width will remain the same.
I think applying a Letterbox resizing is using matrix transformation, so even if your image appears larger, its position and size are still the same. That's why you get the same position as before.
To resolve your problem, you simply have to multiply the coordinates you get (with event.localX or anything else) by the image current scaling and that should be it.
If you already know the final size, you simply have to do something like: newLocalX = event.localX * (resizedImage.width / originalImage.width);
Here some info if you want to know how Matrixes work.
I have been looking to dynamically scale a image map with coordinates to a div, so when re-sizing a window occurs the map and all coordinates are scaled accordingly.
any suggestions on how to do this?
i think this may work
http://blog.outsharked.com/p/image-map-resizer.html
but with the alternate option of :enter a bounding area and the map will be clipped to within that area.
my question then is how do i establish a bounding area, will it scale dynamically to that whole area?
This jQuery plugin works great for scaling and rescaling image maps on the fly. You can call this once, and it will take care of all image maps on the page. It will even rescale an image map if something happens that changes an image's dimensions.
https://github.com/stowball/jQuery-rwdImageMaps.
If you weren't just using the div to solve the image map scaling problem, you could put a blank image (a completely transparent .gif or .png) in your div with the image map applied to it and set its width and height to 100%.
Is it possible to display an image in multiple subplot axes, such that the image appears at the desired scale?
subplot(3,3,[1 4 7]);
%# image scaled down to fit 1 set of axes
imshow(img);
subplot(3,3,2);
plot(relevantData);
%# And so on with 5 other plots
I want to have the image scaled to either a fixed size or to fit the axes available to it, rather than to the size of a single axes.
My use case is to show a video alongside plots derived from the video, such that the plots are progressively drawn in step with the video. Once the display is correct I can save each image and combine them into a video.
Clarification
I am asking if it is possible to produce a figure as described without specifying the position of every element in absolute terms. Though one can make arbitrary figures that way (and in fact I have done so for this project), it is very tedious.
Edit:
For changing the size of the subplot:
In help subplot they mention that you can set parameters on the selected "axes" (that's what they call a plotting area in Matlab).
Using that, you can set the 'position', as seen in help axes. This property takes takes as argument:
[left, bottom, width, height]
As pointed out by #reve_etrange, one should use absolute positioning for axes 'Position'and 'OuterPosition' parameters. they can be in normalized coordinates, though.
For changing the size of the image in the subplot:
I think there are 2 useful things for you in the help imshow output:
'InitialMagnification': setting the magnification of the image.
'Parent': determines which parent imshow will use to put the image in (never tried using imshow with subplots).