I am working with Google earth Engine and I am trying to extract/Filter (clip) pixels in a band using another image (band). I calculated NDVI and created a threshold value that rendered an image with NDVI > 0.3 but I wanted to extract the corresponding pixels in the visible an NIR bands.
Here is snippet code.
var s2 = ee.ImageCollection('COPERNICUS/S2');
var s2_filtered = s2.filterDate('2017-01-01', '2017-12-31')
.filterBounds(geometry) //custom Geometry
var calcNDVI = function(x){
var ndvi4 = x.normalizedDifference(["B5", "B4"]).rename("ndvi")
return x.addBands(ndvi)
}
var ndviCollection = s2_filtered.map(calcNDVI)
var maxNDVI = mosaic.select("ndvi");
var threshold = maxNDVI.gt(0.3)
I am at the point where I wanted to clip the corresponding pixels in "B", "G", "R" and "NIR" bands using the threshold variable(image). Obviously, I'm stuck here. Please let me know if there is with a way to filter/clip pixels of one band using another band with in GEE. The task is similar to using Clipper in QGIS which is the options I am left with if this doesn't work.
Thanks for your help!
The variable threshold is a mask, so you have to mask out pixels in the mosaic using the threshold mask, right? If that is the case, simply update the mask of the image:
var masked = maxNDVI.updateMask(threshold)
Related
I am looking to turn 2 lat/lon positions into an x and y distance of the canvas, then apply the distance formula to it.
Right now I have:
const leftPoint = new LatLon(center.lat, center.lon).destinationPoint(semiMajorAxis, 270);
const rightPoint = new LatLon(center.lat, center.lon).destinationPoint(semiMajorAxis, 90);
const leftXY = Cartographic.toCartesian(Cartographic.fromDegrees(leftPoint.lon, leftPoint.lat));
const rightXY = Cartographic.toCartesian(Cartographic.fromDegrees(rightPoint.lon, rightPoint.lat));
const diameter = distanceFormula(leftXY.x, leftXY.y, rightXY.x, rightXY.y);
But the result of diameter is 18,000, even though both points are on my screen!
Cesium's Cartographic.toCartesian function converts a Cartographic (lon/lat/alt) type of coordinate to a full 3D Cartesian position. Imagine X, Y, Z with zero being the center of the Earth itself, with the Earth's surface being approximately 6.3 million meters in any direction.
If you're looking for 2D canvas / screen coordinates, you must follow this call with another function, Cesium.SceneTransforms.wgs84ToWindowCoordinates. That function converts the 3D WGS84 (Cartesian3) Earth position into a 2D (Cartesian2) screen position. There's a demo of wgs84ToWindowCoordinates being used in the Sandcastle Star Burst Example around line 287.
Also it looks like you've rolled your own LatLon class, not specified above, that appears to have similar functions to Cesium's Cartographic class. You might be able to make the code a little cleaner by using Cartographic directly instead of a homebrew class there. Likewise you don't need to roll your own distanceFormula on the last line. Once you have 2D Cartesian2 window coordinates, call Cesium.Cartesian2.distance to get the distance.
I can't understand your saying 'x and y distance of the canvas'.
Generally, for calculate distance between two point on CesiumJS follow below steps.
1.Define two points
//Define x,y coordinate and convert to radian
const longitudeRadian_1 = Cesium.Math.toRadians(longitudeDegree_1)
const latitudeRadian_1 = Cesium.Math.toRadians(latitudeDegree_1)
const longitudeRadian_2 = Cesium.Math.toRadians(longitudeDegree_2)
const latitudeRadian_2 = Cesium.Math.toRadians(latitudeDegree_2)
//Get cartographic from degrees
const Carto_Point_1 = new Cesium.Cartographic(longitudeRadian_1 , latitudeRadian_1 )
const Carto_Point_2 = new Cesium.Cartographic(longitudeRadian_2 , latitudeRadian_2)
//Get cartesian from cartographic
const Cartesian_Point_1 = Cesium.Cartographic.toCartesian(Carto_Point_1)
const Cartesian_Point_2 = Cesium.Cartographic.toCartesian(Carto_Point_2)
2.Calculate distance between two points
const distance = Cesium.Cartesian3.distance(Cartesian_Point_1, Cartesian_Point_2)
console.log(distance)
I hope this would help
I am trying to create a d3 SVG that draws a map of New York State and scale it so that it fits the size of my SVG, the issue I am having is that when I use .fitSize([height, width], mapObject) it only returns a NaN error in the console.
the topoJSON file of NYS I am using
I am able to get the map to display without scaling but of course, it is not optimized and needs to be scaled
I have attempted what is said in this post but I have not figured out the correct solution
var map = d3.json('./ny.json')
Promise.all([map]).then(data => {
var height = 800;
var width = 800;
var mapData = data[0]
// original geoJSON to that works without scaling
// var geoData = topojson.feature(mapData, mapData.objects["cb_2015_new_york_county_20m"]).features
//
var geoData = topojson.feature(mapData, {
type:"GeometryCollection",
geometries: mapData.objects["cb_2015_new_york_county_20m"].geometries,
})
var projection = d3.geoMercator()
.fitSize([width, height], geoData)
var path = d3.geoPath()
.projection(projection)
d3.select('svg')
.attr('height', height)
.attr('width', width)
.selectAll('.county')
.data(geoData)
.enter()
.append('path')
.classed('.county', true)
.attr('d', path)
})
I am pretty sure this is a formatting error on my part, but I am unsure of what data .fitSize() or .fitExtent() is trying to compare against.
right now the way the code site I receive no error outputted to the console but I also have no data append to the SVG
The issue is that fitSize takes a geojson object while selectAll.data() takes an array, you are using one of these two for both in geoData. This leaves two solutions:
Solution 1:
If we use
var geoData = topojson.feature(mapData, mapData.objects["cb_2015_new_york_county_20m"]).features
var projection = d3.geoMercator()
.fitSize([width, height], geoData)
We get NaN errors because the projection is not set properly as we aren't passing a geojson object, just an array of geojson objects. We could solve this by making a feature collection with geoData and passing that to fitSize:
var geoData = topojson.feature(mapData, mapData.objects["cb_2015_new_york_county_20m"]).features
var projection = d3.geoMercator()
.fitSize([width, height], {type:"FeatureCollection", features: geoData})
Now we are passing a geojson feature collection to fitSize, we're all go on the projection, and since geoData is still an array, we can pass that to selectAll.data() unchanged.
Here's a block.
Solution 2:
If we use:
var geoData = topojson.feature(mapData, {
type:"GeometryCollection",
geometries: mapData.objects["cb_2015_new_york_county_20m"].geometries,
})
We get a geojson object, projection.fitSize works, but selectAll().data(geoData) doesn't add any features as it isn't an array - the enter selection is empty. We can substitute in selectAll().data(geoData.features) to solve this and enter one path per feature (alternatively we could use .data([geoData]) to enter one feature for all the paths).
Here's a block.
Both blocks are drawn at the correct scale - the map exceeds the block bounds as I didn't alter your 800x800 dimensions
I have searched and simply cannot find what I need (if it exists).
A window will have a large picture.
The picture will be divided into zones (such as border lines that separate states on a map).
When a person clicks within a zone, then I will raise the appropriate event.
I've used AS3 with MXML to create a database program. All is working great except for this last step. I cannot figure out how the user is within a particular area of the picture when he clicks or when he touches.
I've read and tried to come up with an approach, and there must be (hopefully so) an easier way than the muddled nonsense I'm coming up with.
Thanks
VL
Are you drawing it in flash professional CS6? If so then why can't you just have the picture as a symbol and then just self divide the lines and make those divided areas into symbols that are children of the picture symbol. You could keep the individual state symbols right where they so that they stay true to the overall picture.
A first thought would be to make an instance of this picture symbol through the code, and then loop though all the children of that picture and add a click event to each one.
var picture:Picture=new Picture();
for(var i:int=0; i<picture.numChildren-1; i++){
picture.getChildAt(i).addEventListener(MouseEvent.CLICK, mouseEventHandler);
}
Please comment if I am missing something, or this does not work.
EDIT
Well, if you know the dimensions of the image, you could divide its width and height by 3(your number of rows and columns) and this is your zone dimensions. You then could take the mouse's click point relative to the top left of your picture and then divide its width by the zone with, and its height by the zone height, and then get its integer floor value, you could get which region it is. Code it below:
//This is all for a constat region list (like a window, or floor tiles, not things irregular)
import flash.display.Sprite;
var regionsX:int = 3; //Your number of windows across the row
var regionsY:int = 3; // across the column
var regions:Array = new Array(); // an array to hold the values that you will get from where the user clicks
// All of this used a 2D array method
for(var x:int = 0; x < regionX; x++) {
regions[regionsX] = new Array();
for(var y:int = 0; y < regionY; y++) {
regions[regionsX][regionsY] = "region(".concat(x).concat(",").concat(y);
// Here you make this equal to anything you want to get a value of,
//once the correct region is found (I just have a string version here for an example)
}
}
... // other stuff..
var picture:Picture = new Picture(); // your window picture
var regionWidth:Number = picture.width / regionsX; // Gets each region's width
var regionHeight:Number = picture.height / regionsY; // Get each regoin's height
...
picture.addEventListener(MouseEvent.CLICK, mouseEventListener); // add a click listener to the picture
function mouseEventListener(event:MouseEvent):void{
var mouseX:Number = picture.globalToLocal(event.stageX); // gets where the user clicked, and then converts it
//to the picture's cordinate space. ( 50,100 acording to the stage, could be (25,200) to the picture)
var mouseY:Number = picture.globalToLocal(event.stageY); // same for the Y
var regionIntX:Number = Math.floor(mouseX / regionWidth); // Dives the point by each region's width, and then
// converts it to a while integer. (For instance, if a region's width is 100 and you click at 288, then if you do the
// math, you clicked in the 3rd region, but it returns 2... why? (becaue the array counter starts at 0, so 0 is the 1st
// region, 1 is the second and so on...
var regionIntY:Number = Math.floor(mouseY / regionHeight); // Same for Y
var yourValue:String = regions[regionIntX][regionIntY]; // This returns that you initialy put into your 2d array
// by using the regionIntX and regionIntY for the array values. You have to decide what is stored in this array...
}
The simplest solution would be to add an event listener for MouseEvent.CLICK to the picture and in the handler check properties mouseX and mouseY of the picture. Define the bounds of each area in an XML or similar and check against current mouseX/Y to see which area has been clicked.
I have an Image that's 5000 pixels by 5000 pixels. It's scaled up and down regularly to fit different parts of the image into the window.
I'm making a function that focuses in on different places on the image (like a map) and then zooms into a certain scale that I specify.
I pass my point into this function (new Point(2000,2500) for example)) however this always breaks because it's not relative to the image specifically.
How do I make the Point relative to the image at the image's given scale at any given time?
Additional Info: I'm using the guide here http://www.adobe.com/devnet/flex/samples/fig_panzoom.html for panning and zooming functionality.
Solved:
One of my pitfalls was that I was using a possible bitmapScaleFactor > 1 which would mess up the scaling. This was the final function that worked for my usage.
protected function testFocus(p:Point):void
{
var content:ContentRectangle = boardViewer._contentRectangle;
var panToPoint:PanToPointCommand = new PanToPointCommand(boardViewer, content);
var scale:Number = boardViewer.bitmapScaleFactor;
var location = new Point((p.x*scale)+content.x, (p.y*scale)+content.y);
var center = new Point(boardViewer.width/2, boardViewer.height/2);
//Move the point to the center
panToPoint.fromPoint = location;
panToPoint.toPoint = center;
panToPoint.execute();
}
I've not tested this but how about using the scale factor that is being applied to the image to alter the point coordinates.
e.g.
var scaler:Number = 0.5;
image.scaleX = image.scaleY = scaler;
new Point(2000*scaler,2500*scaler);
Are you looking for DisplayObject.mouseX/mouseY? These do not take any rotation into account, however.
To take rotation into account, you could do something like (untested code):
var mat:Matrix = image.transform.concatenatedMatrix;
mat.invert();
// now use mat to transform point from 'stage space' to 'image space'
var pImage:Point = mat.transform(new Point(stage.mouseX, stage.mouseY));
I'm learning ActionScript/Flash. I love to play with text, and have done a lot of that kind of thing with the superb Java2D API.
One of the things I like to know is "where, exactly, are you drawing that glyph?" The TextField class provides the methods getBounds and getCharBoundaries, but these methods return rectangles that extend far beyond the actual bounds of the whole text object or the individual character, respectively.
var b:Sprite = new Sprite();
b.graphics.lineStyle(1,0xFF0000);
var r:Rectangle = text.getCharBoundaries(4);
r.offset(text.x, text.y);
b.graphics.drawRect(r.x,r.y,r.width,r.height);
addChild(b);
b = new Sprite();
b.graphics.lineStyle(1,0x00FF00);
r = text.getBounds(this);
b.graphics.drawRect(r.x,r.y,r.width,r.height);
addChild(b);
Is there any way to get more precise information about the actual visual bounds of text glyphs in ActionScript?
Richard is on the right track, but BitmapData.getColorBounds() is much faster and accurate... I've used it a couple of times, and optimized for your specific needs its not as slow as one might think.
Cory's suggestion of using flash.text.engine is probably the "correct" way to go, but I warn you that flash.text.engine is VERY (very!) hard to use compared to TextField.
Not reasonably possible in Flash 9 -- Richard's answer is a clever work-around, though probably completely unsuitable for production code (as he mentions) :)
If you have access to Flash 10, check out the new text engine classes, particularly TextLine.
I'm afraid all the methods that are available on TextField are supposed to do what you have already found them to do. Unless performance is key in your application (i.e. unless you intend to do this very often) maybe one option would be to draw the text field to a BitmapData, and find the topmost, leftmost, et c colored pixels within the bounding box retrieved by getCharBoundaries()?
var i : int;
var rect : Rectangle;
var top_left : Point;
var btm_right : Point;
var bmp : BitmapData = new BitmapData(tf.width, tf.height, false, 0xffffff);
bmp.draw(tf);
rect = tf.getCharBoundaries(4);
top_left = new Point(Infinity, Infinity);
btm_right = new Point(-Infinity, -Infinity);
for (i=rect.x; i<rect.right; i++) {
var j : int;
for (j=rect.y; j<rect.bottom; j++) {
var px : uint = bmp.getPixel(i, j);
// Check if pixel is black, i.e. belongs to glyph, and if so, whether it
// extends the previous bounds
if (px == 0) {
top_left.x = Math.min(top_left.x, i);
top_left.y = Math.min(top_left.y, j);
btm_right.x = Math.max(btm_right.x, i);
btm_right.y = Math.max(btm_right.y, j);
}
}
}
var actualRect : Rectangle = new Rectangle(top_left.x, top_left.y);
actualRect.width = btm_right.x - top_left.x;
actualRect.height = btm_right.y - top_left.y;
This code should loop through all the pixels that were deemed part of the glyph rectangle by getCharBoundaries(). If a pixel is not black, it gets discarded. If black, the code checks whether the pixels extends further up, down, right or left than any pixel that has previuosly been checked in the loop.
Obviously, this is not optimal code, with nested loops and unnecessary point objects. Hopefully though, the code is readable enough, and you are able to make out the parts that can most easily be optimized.
You might also want to introduce some threshold value instead of ignoring any pixel that is not pitch black.