CODEWITHSUNDEEP
androidcanvasbitmap
Direz
Direz

Reputation: 7

Drawing on bitmap vs directly on canvas

In my application I need to draw a large network (basically, little boxes connected with lines) and the user will be able to zoom and pan it around.

My first option was to draw the network directly to the canvas, but I thought that was not very efficient, because each time a pan event occurs, the drawing process begins again.

So I tried to use a large mutable bitmap and draw my entire network only once (or at least whenever zoom occurs), and blit the necessary areas to the canvas.

My problem is, since the network is rather big, I get OOM exception when creating the bitmap…

What should I do? Draw directly to the canvas? Use several smaller bitmaps?

Thanks, Direz

Upvotes: 0

Views: 1577

Answers (2)

Daniel Werner
Daniel Werner

Reputation: 128

You're probably not going to like this, but if all you're doing is drawing boxes and lines, the efficiency of the canvas is going to be pretty dang high. Are you getting UI lag or something?

One thing I have messed around with is drawing collections of subcomponents that won't change much or at all to a bitmap then rendering (scaling/moving aren't all that expensive if done at the right level) to the canvas can help efficiency. I have tried in the past to create a framework for rendering a tile-like subset of an existing larger image, but did not meet much success. I've made things work, but the code just gets ugly.

Oh, also a quick test to see if the component you are rendering is within the rectangle created by the screen can save you a bunch of processor time.

Upvotes: 0

Delete
Delete

Reputation: 922

My first question to you is how many sprites you have going at once? By far, the fastest mechanism for having many sprites on the screen is to use OpenGL due to the hardware accelleration. The besy way, on Android, I have found to do this is to use the Cocos2d android (not to be confused with the ios version) which is available on Google Projects. You will have to use the IOS documentation in order to understand it though and there are a few decent tutorials to get started with online..in particular, the hello world template here... Www.sketchydroide.com/Blog/p?=8. It is out of date compared to the latest IOS cocos2d but thats to be expected. I have found that the programs run MUCH faster when not connected to an active debugger session in my experiments.

If you want to stick with your current approach or the above is still not fast enough, you are going to have to attempt to cull any drawing which does not appear n the screen meaning a general function of the form "if the sprite's x and y values are outside the bounds of the visible area, dont draw it" which is basically how most tile base games handle the issue.

It sounds like you are doing the drawing manually if you are doing little squares. I think it is more adviseable to go ahead and draw on the canvas but to be very careful about managing your sprite counts and to avoid heavy for loop iteratiins that occur on the frame update loops where possible. It is rather easy to max out your little handset with drawing operations.

Another option might be to draw the entire bitmap once into memory and then use a copy rectangle operation to transfer the image to the screen without drawing the full bitmap you have created. I think that copy rect should be a fast operation normally but if you are using it to draw the whole screen it seems like overkill and probably wont work as well.

Upvotes: 1

Related Questions