CODEWITHSUNDEEP
c#performancememorycontrols
ahmedsafan86
ahmedsafan86

Reputation: 1794

How to render a very large image or document that is drawn without any performance issues

I want to make a control that acts as a time ruler with a wave form for sound wav files like that in movie maker or in camtasia studio video editor

the problem is that the duration is long how to render all of it??one time or when the user is scrolling to a point if it isn't rendered I'll render it? what after its all rendered ? it will be so long user will zoom in and so on how to do it without effecting the performance

Upvotes: 0

Views: 327

Answers (2)

Wolf5370
Wolf5370

Reputation: 1374

We do not know how you are rendering your graphic, but I presume you are using unsafe lockbits to generate directly into a bitmap. As Maciej says, just render the part you need to display - when zoomed, either render again (should be fast). You can preempt by rendering current, zoom in 1, zoom out 1, left 1/2 a screen, right 1/2 screen etc in the background, but then you need to manage these (they can be rendered in parallel of course using background worker threads). The key to memory is to keep the bitmaps to a minimum (you have the algorithm of the graph and the renderer) and the key to speed is to keep it low level and prefetch what you can and parallelism.

Upvotes: 1

Maciej
Maciej

Reputation: 7961

If you're dealing with a big image and lots of data I would sugest this:

  • render/display what user is currently looking at
  • render rest of if in a background thread into a memory image

Once you have the whole image rendered in an image kept in memory, any scrolling and/or zooming would be just to position your display window.

Render your image in an unzoomed scale into a Bitmap object. When you need to display part of if use Bitmap.Clone to copy section of that bitmap into a picture displayed to user. A bit difficult part will be to render part of your base Bitmap which is currently demanded to be viewed.

This could be memory demanding. It is effectively a caching mechanism and as always in cases like that you get speed by using more memory.

Something similar to how google maps works.

Upvotes: 1

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