Graphics performance optimization issue

Question

Here's the problem :

I need to scroll a huge image of a wave form that has been rendered previously, WPF didn't let me assign that huge (80000*256) picture to an Image, it works for smaller (30000*256) images but it's so slow animating it that it's unpractical.

So what I decided was to use a WriteableBitmap that I assign to my Image.Source, and then I only have to update say 1920*256 (or only the width of the screen). It works much better now but after some profiling, it seems that the actual copying process takes quite some time and it's not 60 fps everytime.

I am already writing to the bitmap by locking it and using pointers.

My question is :

Do you know any (faster) way to update a bitmap ?

These pixels are already in memory in the huge bitmap, reading straight from here seems a wise idea; well, get rid of the WriteableBitmap between my Image.Source and my BitmapData.

Thanks for your help :)

Answer 1

You can try using BitmapSource.CopyPixels to extract the bytes with color information from the image (not sure if you need that) and BitmapSource.Create that creates a bitmap from a byte array (or its overload which can grab color information directly from unmanaged memory).

Answer 2

You can try using InteropBitmap to update the pixels as WriteableBitmap is kind of slow with its CPU bound internal operations. I have some code here that uses it: http://silverlightviewport.codeplex.com/SourceControl/changeset/view/57274#1534506

It's hardcoded for Bgra32, which is the only color space supported by InteropBitmap in 3.5 SP1. In 4.0 it should support 24 bit color spaces.

Answer 3

Hello everyone,

I have fixed it, using GC.Collect; still can't believe it fixed the problem. Don't know if it's a good practice but it works ...

That gave me headaches and nightmares the last few days but now most is sorted. The funny conclusion I'll have about this, is that GCCollectionMode.Optimized, thinks it's never the time to collect memory, it went up to use 2Gb, destabilizing the whole system (Windows) up to the point it freezes the mouse, lol ...

Thanks for your help :-)