I am trying to extract a colored polygon from a map img. Lets say for example this img
Could it be possible to put this img on lets say the top of google map and create some sort of script that could reproduce this polygon using the coordinates from a real map.
I was thinking of using 2 reference points from the img and the actual map, putting them one on top of the other, and extract the polygon by the color that outlines it.
That would be done on PHP.
Related
Using PHP, we have an array of GPS coordinates that create a specific route.
I need to allow the user to give an input width. Using this input we need to create a polygon around the line.
In the image found under the link below:
https://drive.google.com/file/d/1DmVdKAh6advlcQYiDZQPsKYisjxmPu5I/view?usp=sharing
We are given the latitude and longitude of the points A,B,C. I need a way to get the coordinates of the points D,E,F,G,H. Note that these are GPS locations and not 2d formulas
I am using Google Maps to display locations stored in a MySQL database containing name, latitude and longitude information. An AJAX request is sent and the map is updated with all the locations. So far, so good.
Users have the ability to filter the locations by drawing polylines on the map to create a bounding box. The idea is that only locations within this bounding box are returned and they can draw whatever shape they want.
All the points used to draw the shape are returned a list of coordinates. Where I am struggling is taking the list of coordinates and finding everything within them. Can I achieve this with an SQL query? Is it even possible?
I have seen examples of returning locations within x radius from one set of coordinates and also a square box, but I have no idea how to take that further and get everything within a potentially infinite set of coordinates.
You should transform the shape the user enters into a polygon. Then you transform all locations within a square around this polygon into the same coordinate system.
Using a solution describe in the wikipedia page for point-in-polygon problems you will be able to find all locations within this shape and remap them to coordinates in your sql database and then into locations.
There are however similar question which might help you find a proper solution to your problem. See:
How can I determine whether a 2D Point is within a Polygon?
Point in Polygon Algorithm
I need to get programmatically polygon points coordinates from image.
Here is an example: http://imgur.com/gbs96tt
Is there any libraries or any solutions for this? Desirable written in php.
I am looking to achieve:
http://i53.tinypic.com/2gule04.jpg
I have tried the answers mentioned at Curving an image that starts as a rectangle (uploaded by user), preferably using Canvas or JS
Based on the answers there, I have tried pixel wise transformation which didn't work. To understand a mesh based approach, you will need a skill set of 3d-2d developer which I don't possess.
I am a PHP developer and I am looking for an answer in either PHP or HTML5. I have tried number of things ranging from HTML5 canvas to splitting the image into smaller parts and then joining them however those don't seem to work.
A help in the right direction will be greatly appreciated.
If you can use ImageMagick, the Circular and Radial Distortion Methods examples should come pretty close.
I don't know whether the PHP ImageMagick extension (as opposed to calling ImageMagick from the command line) supports this as well, but it might.
To achieve a similar effect you want to try texture mapping and you need some 2d-3d subdivision and math skills. Basically the idea is to subdivide the texture in triangles and map them to the 2d coordinate using a transformation matrix. It's simplier to start with rectangles first and then use your curved form but I'm new to this too, so I don't know really if texture mapping is used at all to curve an image. Here is an example of a simple texture mapping: Image manipulation and texture mapping using HTML5 Canvas?.
In the aforementioned link there is this sub function:
n the following code I assume you have a picture object texture and 4 corners each of
which is an object with fields x,y,u,v where x,y are pixel coordinates on the target canvas and u,v are pixel coordinates on texture:
IMO this is information enough to start with texture mapping.
A posibility is to use rotoscopic animation instead of mathematical tweening. In other words, you can achieve such transformation with 5 or 6 (or as many as you want) frames that are sequentially drawn on the HTML5 canvas at your desired frame-rate.
You can easily draw each frame using Canvas native API. In your case, you just need to draw Text and then a closed path like:
ctx.beginPath();
ctx.moveTo(...);
ctx.arc(...);
ctx.lineTo(...);
ctx.arc(...);
ctx.lineTo(...);
ctx.closePath();
and just adjust the corresponding values for each frame.
It should be pretty easy!
I'm working on a PHP application that needs to obtain data from a topographical map (different elevations denoted by different colors). I need to do two things:
Using this map (800x600), find a way to determine the exact pixel location of a particular city. For example, San Francisco is located at precisely 121x585.
Using the location from (1) above, I need to read the exact color at that location.
Note: The map provider does not provide location-based data, only a colored map. I suspect multiple libraries would be needed to map coordinates to locations on the map (via a ratio?) and then use OCR to read the color.
Are there any PHP libraries/tools that do this? How would you pull this off?
Once you know the pixel-coordinates, you can use PHP's built-in GD library to sample the color of an arbitrary pixel quite easily.
The tricky bit will be determining the pixel to sample, which can get pretty darned tricky. The earth being sphere-like, maps use various projections to produce a 2-d representation. If you know how the colored map image is projected, and you know the latitude/longitude of the pixel at (0,0), you should be able to write a function to convert lat/long to a pixel coordinate.
I may not have understood the problem entirely, but you should map the locations you want into an array (of objects?)
$city_mapping = array(new City("San Francisco", 121, 585), new City....); //Map your cities to an array.
Where City should be defined as a class to contain those variables.
Then use imagecolorat() to check for the color.