I would like to be able to fill a shape with a canvas; potentially to have one konva canvas generate an animation and update another konva canvas shape with it, masked inside a path. Is this possible?
Its not totally clear what you actually want to do, but what you describe is probably achievable with Konva layers. You see Konva is a wrapper for HTML5 canvas and one of its features is layers - so you have one Konva instance that must have a minimum of one layer but can have more. Konva cunningly uses a separate HTML5 canvas for each layer. See the example here in the Konva docs. If you hit F12 you can see the two canvas elements used, and there is a code sample too.
This gives a lot of power and some great performance management potential. And it is all baked in to Konva already so you will not have to manage multiple canvas instances in your own code.
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I have hundreds of shapes in canvas when onClick on a shape will take an action.
In my feature test, I am currently simulating the mouse click on a particular pixel. However, this is not ideal because the position of the graph may change. Unlike SVG, canvas doesn't expose the particular shape in the DOM. Is there a way to select the shape in a canvas by id for testing purposes?
You can use selectors to find any node inside the stage https://konvajs.org/docs/selectors/Select_by_id.html
const shape = stage.findOne('#id');
Need to develop the component shown in the image above using Objective-C language. No idea where to start and which framework to use. Any heads up/reference links to develop this component is highly appreciated.
Use a combination of UIBezierPaths with custom fill colors. You can either use a shape layer or core graphics. Bezier path allows you to construct a custom path, so the first one will be a triangle, and the second a quadrilateral.
You could also use paint code if you want to construct the path visually.
Look at this
https://www.raywenderlich.com/76433/how-to-make-a-custom-control-swift
It's a very general way to create whatever control you want.
I'm trying to create an iOS recoloring app (this is my reference), and i need to know how recolor some portion of the image when user taps on a given area. All the loaded pictures will be black/white initially.
Is there any prebuilt library? Or which graphics framework should i use?
Any help will be appreciated.
If what you are looking for is adding/replacing the colour within a certain shape and edges are really important (as in the example) then you should be looking into vectorised drawing.
What this means is every shape in your image would have an actual object representation in your code, and you could easily interact with that object to do whatever you want (i.e. tap gestures to change colour, zoom etc.).
This however, means that you can't simply use .jpeg images, and you need to use images in vector format, such as .svg or CorelDraw.
As a reference, check out SVGKit, which is an excellent library for working with SVG images.
I'm working on a graphing application which I wrote using Core Graphics. I have a buffer which accumulates data, and I render it on the screen. It's super slow and I want to avoid going to openGL if possible. According to the profiler, drawing my graph data is what's killing me (which consists of a number of points which are converted to a path, followed by the calls AddPath, DrawPath)..
This is what I want to do, my question is how to best implement it using layers / views / etc..
I have a grid and some text. I want this to be rendered in a CALayer (or some other layer/view?) and only update when required (the graph is rescaled).
Only a portion of the data needs to be refreshed. I want to take the previous screen buffer, erase a rectangle's worth of data (or cover it with a white box) and then draw only the portion of the graphs that have changed.
I then want to merge the background layer with the foreground graphs to generate the composite image. This requires the graph layer to have a transparent background so as not to obscure the grid.
I've looked at using CAlayer as a sublayer, but it doesn't seem to provide a simple way to draw a line. CAShapeLayer seems a bit better, but it looks like it can only draw a single line. I want the grid to be composed of multiple lines.
What's the best approach and combination of objects to allow me to do this?
Thanks,
Reza
I'd have a CGLayerRef that was used for drawing the path into. For each new point I'd draw just the new segment. When the graph got to full width I'd create a new CGLayerRef and start drawing the new line segments into that.
What happens to the previous layer as it's drawn over by the new layer depends on how your graph is displayed, but you could clear the section which is now underneath the new layer (using CGContextSetBlendMode(context, kCGBlendModeClear);) or you could choose to blend them together in some other way.
Drawing the layers each time you make a change to the lines they contain is relatively cheap compared to drawing all of the line segments themselves.
Technically, there would also be CALayers used to manage the drawing of the CGLayerRefs to the screen (via the delegate relationship drawLayer:inContext:), but all of the line drawing is done using the CGLayerRefs context and then the CGLayerRef is drawn as a whole into the CALayers context (CGContextDrawLayerInRect(context, frame, backingCGLayer);).
I am building a 3D image viewer which has Three.JS plane geometries as placeholders with the images as their textures.
Now I want to add a black border around the image. The only way I have found yet to implement this is to add a new black plane geometry behind the image to be displayed. But this required whole-sale changes to my framework which I want to avoid.
WebGL's texture loading function gl.texImage2D has a parameter for border. But I couldn't find this exposed anywhere through Three.js and doubt that it even works the way I think it does.
Is there an easier way to add borders around textures?
You can use a temporary regular 2D canvas to render your image and apply any kind of editing/effects there, like paint borders and such. Then use that canvas image as a texture. Might be a bit of work, but you will gain a lot of flexibility styling your borders and other stuff.
I'm not near my dev machine and won't be for a couple of days, so I can't look up an example of my own. This issue contains some code to get you started: https://github.com/mrdoob/three.js/issues/868