I have a problem. I followed this tutorial about touchmanipulations in skiasharp: https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/graphics/skiasharp/transforms/touch and it's working great. But for example scaling only works if both my fingers hit the bitmap. The problem is that if the bitmap is very small, I won't be able to scale it. How can I focus on the bitmap with my primary finger and use my secondary finger from anywhere on the canvas to Scale it?
My full code is in that page!
Any idea?
Had refered image apps like Google photos and others. My opinion is there can be two improvements in your image component.
Handle touch of the background view instead of the image view.
Restrict scaling lower than a minimum scale value. Very low scale values doesn't have a use case as the end user cannot view it.
I'm not sure of your use case implementing the second improvement is entirely up to your decision
Related
I am building a web application which will display a large number of image thumbnails as a 3D cloud and provide the ability to click on individual images to launch a large view. I have successfully done this in CSS3D using three.js by creating a THREE.CSS3DObject for each thumbnail and then append the thumbnail as an svg:image.
It works great for upto ~1200 thumbnails and then performance starts to drop off (very low FPS and long load time). By the time you hit 2500 thumbnails it is unusable. Ideally I want to work with over 10k thumbnails.
From what I can tell I would be able to achieve the same result by creating each thumbnail as a WebGL mesh with texture. I am a beginner with three.js though, so before I put in the effort I was hoping for guidance on whether I can expect performance to be better or am I just asking too much of 3D in the browser?
As far as rendering goes, CSS3 should be relatively okay for rendering quite big amount of "sprites". But 10k would probably be too much.
WebGL would probably be a better option though. You could also take care about further optimizations, storing thumbnails in atlas texture or such...
But rendering is just one part. Event handling can be serious bottleneck if not handled carefully.
I don't know how you're handling mouse clock event and transition towards fullsize image, but attaching event listener to each of 2.5k+ objects probably isn't a good choice anyway. With pure WebGL you could use imagespace for detecting clicked object. Encoding each tile with different id/color and using that to determine what's clicked. I imagine that WebGL/CSS3D combo could use this approach as well.
To answer question, WebGL should handle 10k fine. Maybe you'll need to think about some perf optimization if your rectangles are big and they take a significant amount on the screen, but there are ways around it if that problem appears.
As an exercise, I decided to write a SimCity (original) clone in Swift for OSX. I started the project using SpriteKit, originally having each tile as an instance of SKSpriteNode and swapping the texture of each node when that tile changed. This caused terrible performance, so I switched the drawing over to regular Cocoa windows, implementing drawRect to draw NSImages at the correct tile position. This solution worked well until I needed to implement animated tiles which refresh very quickly.
From here, I went back to the first approach, this time using a texture atlas to reduce the amount of draws needed, however, swapping textures of nodes that need to be animated was still very slow and had a huge detrimental effect on frame rate.
I'm attempting to display a 44x44 tile map where each tile is 16x16 pixels. I know here must be an efficient (or perhaps more correct way) to do this. This leads to my question:
Is there an efficient way to support 1500+ nodes in SpriteKit and which are animated through changing their textures? More importantly, am I taking the wrong approach by using SpriteKit and SKSpriteNode for each tile in the map (even if I only redraw the dirty ones)? Would another approach (perhaps, OpenGL?) be better?
Any help would be greatly appreciated. I'd be happy to provide code samples, but I'm not sure how relevant/helpful they would be for this question.
Edit
Here are some links to relevant drawing code and images to demonstrate the issue:
Screenshot:
When the player clicks on the small map, the center position of the large map changes. An event is fired from the small map the central engine powering the game which is then forwarded to listeners. The code that gets executed on the large map the change all of the textures can be found here:
https://github.com/chrisbenincasa/Swiftopolis/blob/drawing-performance/Swiftopolis/GameScene.swift#L489
That code uses tileImages which is a wrapper around a Texture Atlas that is generated at runtime.
https://github.com/chrisbenincasa/Swiftopolis/blob/drawing-performance/Swiftopolis/TileImages.swift
Please excuse the messiness of the code -- I made an alternate branch for this investigation and haven't cleaned up a lot of residual code that has been hanging around from pervious iterations.
I don't know if this will "answer" your question, but may help.
SpriteKit will likely be able to handle what you need but you need to look at different optimizations for SpriteKit and more so your game logic.
SpriteKit. Creating a .atlas is by far one of the best things you can do and will help keep your draw calls down. Also as I learned the hard way keep a pointer to your SKTextures as long as you need them and only generate the ones you needs. For instance don't create textureWithImageNamed#"myImage" every time you need a texture for myImage instead keep reusing a texture and store it in a dictionary. Also skView.ignoresSiblingOrder = YES; helps a bunch but you have to manage your own zPosition on all the sprites.
Game logic. Updating every tile every loop is going to be very expensive. You will want to look at a better way to do that. keeping smaller arrays or maybe doing logic (model) updates on a background thread.
I currently have a project you can look into if you want called Old Frank. I have a map that is 75 x 75 with 32px by 32px tiles that may be stacked 2 tall. I have both Mac and iOS target so you could in theory blow up the scene size and see how the performance holds up. Not saying there isn't optimization work to be done (it is a work in progress), but I feel it might help get you pointed in the right direction at least.
Hope that helps.
I'm very new to bootstrap, and programming in general so please be patient! I have literally spent hours trying to find a solution to my problem via here/google, and the time has come to ask for some help!
Basically, I am trying to make a website for displaying photos in a carousel. I want my site to be responsive so it works on smaller devices. All my original images are the same size/dimensions (2304 x 1728 so 4:3, probably too big) and use the img-responsive class.
It looks fine on a large screen, but when I try it on smaller laptop screens and tablets, the image height causes scrollbars to appear so you can't see the bottom of the image/caption. However, the image width is responsive and shrinks to fit without scrolling.
I am of the understanding that the carousel size is dictated by the image size, so the logical solution would be to make my image size smaller in height - but I need to maintain the aspect ratio, and smaller images didn't look so good. I also tried setting a fixed height as a style but it didn't work.
What is the ideal image size (in px) for a carousel which takes up most of a browser window (allowing for navbar/header/footer), and how do you make it so the height doesn't require scrollbars?
Many thanks in advance!
My answer may not be accepted by everyone , but I think the only flaw of bootstrap is precisely the Bootstrap Carousel
Can not be changed easily (since as you say you do not have much programming experience), and does not offer a lot of customization
So I think the best solution for your problem is Owlcarousel , offers hundreds of customization options
OWL Carousel
Touch enabled jQuery plugin that lets you create beautiful responsive carousel slider.
I'm sorry if my question is somewhat vague. It's been a few years since I did anything with Qt, and back then I never did any fancy image stuff. What I'm asking for below is just some general suggestions on which classes to consider using. I'm trying to avoid barking up the wrong tree from the very start.
The situation: I'm writing a Qt-based program in which I need to display a somewhat large (let's say 5000x5000) raster image. The user should be able to zoom (quickly) in and out, and pan around the image in a way similar to for example Google maps. So far, this is not very different from the Qt ImageViewer example, except perhaps for the requirement that zooming happens quickly. However, I need to draw on the order of 50k simple geometric shapes (let's say circles) on top of the image, and be able to add and remove some of these in a simple way. The circles should have the same size no matter the zoom level, and should thus either be redrawn whenever the user zooms, or should be drawn with vector graphics. Think of the circles as map annotations. These should look the same at any zoom level, and also behave nicely with respect to panning.
I guess my question is twofold:
Can Qt draw vector graphics on top of a raster image?
In general, which classes should I consider for the above?
Thanks in advance. I don't like answering vague questions myself, but maybe someone with experience with Qt's graphics capabilities has an answer.
I suggest you use QGraphicsView and friends for this. It helps handling all the view/world transformation and the vector items can be achieved with various QGraphicsItems.
You can change the sizes of the items whenever the zoom level changes to maintain constant apparent sizes.
I'm planning on writing a game using javascript / canvas and I just had 1 question: What kind of performance considerations should I think about in regards to loading images vs just drawing using canvas' methods. Because my game will be using very simple geometry for the art (circles, squares, lines), either method will be easy to use. I also plan to implement a simple particle engine in the game, so I want to be able to draw lots of small objects without much of a performance hit.
Thoughts?
If you're drawing simple shapes with solid fills then drawing them procedurally is the best method for you.
If you're drawing more detailed entities with strokes, gradient fills and other performance sensitive make-up you'd be better off using image sprites. Generating graphics procedurally is not always efficient.
It is possible to get away with a mix of both. Draw graphical entities procedurally on the canvas once as your application starts up. After that you can reuse the same sprites by painting copies of them instead of generating the same drop-shadow, gradient and strokes repeatedly.
If you do choose to draw sprites you should read some of the tips and optimization techniques on this thread.
My personal suggestion is to just draw shapes. I've learned that if you're going to use images instead, then the more you use the slower things get, and the more likely you'll end up needing to do off-screen rendering.
This article discusses the subject and has several tests to benchmark the differences.
Conculsions
In brief — Canvas likes small size of canvas and DOM likes working with few elements (although DOM in Firefox is so slow that it's not always true).
And if you are planing to use particles I thought that you might want to take a look to Doodle-js.
Image loading out of the cache is faster than generating it / loading it from the original resource. But then you have to preload the images, so they get into the cache.
It really depends on the type of graphics you'll use, so I suggest you implement the easiest solution and solve the performance problems as they appear.
Generally I would expect copying a bitmap (drawing an image) to get faster compared to recreating it from primitives, as the complexity of the image gets higher.
That is drawing a couple of squares per scene should need about the same time using either method, but a complex image will be faster to copy from a bitmap.
As with most gaming considerations, you may want to look at what you need to do, and use a mixture of both.
For example, if you are using a background image, then loading the bitmap makes sense, especially if you will crop it to fit in the canvas, but if you are making something that is dynamic then you will need to using the drawing API.
If you target IE9 and FF4, for example, then on Windows you should get some good performance from drawing as they are taking advantage of the graphics card, but, for more general browsers you will want to perhaps look at using sprites, which will either be images you draw as part of the initialization and move, or load bitmapped images.
It would help to know what type of game you are looking at, how dynamic the graphics will need to be, how large the bitmapped images would be, what type of framerate you are hoping for.
The landscape is changing with each browser release. I suggest following the HTML5 Games initiative that Facebook has started, and the jsGameBench test suite. They cover a wide range of approaches from Canvas to DOM to CSS transforms, and their performance pros and cons.
http://developers.facebook.com/blog/post/454
http://developers.facebook.com/blog/archive
https://github.com/facebook/jsgamebench
If you are just drawing simple geometry objects you can also use divs. They can be circles, squares and lines in a few CSS lines, you can position them wherever you want and almost all browser support the styles (you may have some problems with mobile devices using Opera Mini or old Android Browser versions and, of course with IE7-) but there wouldn't be almost any performance hit.