Question

Writing bits to screen in Direct Draw

Asked by: Evlich

I have an array of bytes which encode pixel values (they are palettized) and I want to draw this to the screen as fast as possible. Basically my function looks like this:

void __fastcall
draw(__int8* line, int lineCount)
{
// Line points to an array of bytes where each byte encodes 2 pixel values, e.g.
// line -> [0x0F, 0x52, ...] Is pixels 0,F,5,2
//           A single line of the array is guarnateed to be exactly 128 bytes (corresponding to 256 pixels)
// lineCount is the number of lines that the buffer points to
}

void __fastcall
endDraw()
{
// Once I accumulate 240 lines, I need the data to actually go onto the screen
// I'm using DirectX (DirectDraw) and am hoping that all that I have to do here is call flip on my primary surface.
}

If there is a better format for the data to be in, that can possibly be managed, but since the surface can only show 16 colors I was thinking that this would be a good format.

The target platform is going to be a PocketPC-type device which is the reason that I'm not using D3D.

Thanks in advance.

This Question has been solved and asker verified All Experts Exchange premium technology solutions are available to subscription members.

Subscribe now for full access to Experts Exchange and get

Instant Access to this Solution

  • Plus...
  • 30 Day FREE access, no risk, no obligation
  • Collaborate with the world's top tech experts
  • Unlimited access to our exclusive solution database
  • Never be left without tech help again

Subscribe Now

Asked On
2007-05-22 at 04:31:16ID22586790
Tags

directdraw

,

screen

,

draw

Topics

Windows Mobile (Pocket PC / Win CE) Operating Systems

,

DirectX Graphics & Game Programming

Participating Experts
2
Points
500
Comments
5

Trusted by hundreds of thousands everyday for fast, accurate and reliable tech support.

  • "The time we save is the biggest benefit of Experts Exchange to Warner Bros. What could take multiple guys 2 hours or more each to find is accessed in around 15 minutes on Experts Exchange." Mike Kapnisakis, Warner Bros.
  • "Our team likes having a resource that is more secure than just using Google and most experts using this service really know their stuff. It's nice to look here first versus using Google." Dayna Sellner, Lockheed Martin
  • "Anytime that I've been stumped with a problem, 9 out of 10 times Experts Exchange has either the accepted solution or an open discussion of the potential solution to the problem." Kenny Red, eBay Inc.

See what Experts Exchange can do for you.

Got a question?

We've got the answer.

Experts Exchange has been collecting answers to technology questions since 1996…3 million and counting! If you have a question, chances are we already have your answer.

Screenshot of Experts Exchange Knowledgebase

Need individual assistance?

Our experts are ready to help.

If you can't find the exact answer you're looking for, ask our exclusive community of 50,000 experts. You’ll get a personalized answer from a trusted professional.

Screenshot of Experts Exchange Knowledgebase

Want to learn from the best?

Read articles from industry experts.

Thousands of free tech tips, tricks, how-to’s and tutorials are available in our peer reviewed articles section. See for yourself how smart our experts are, no login required.

Screenshot of an Article

Working on a long term project?

Store your work and research.

Save solutions to your questions, answers you’ve discovered through searching plus helpful articles in your personal knowledgebase for easy future access.

Screenshot of Experts Exchange Knowledgebase

Access the answers to your technology questions today.

Subscribe Now

30-day free trial. Register in 60 seconds.

What Makes Experts Exchange Unique?

Members of the expert community talk about why the experience at Experts Exchange is different than what you will find anywhere else.

Trusted by the world's most respected brands.

image of each brand's logo

Faithfully serving IT professionals since 1996.

Experts Exchange Logo

Try it out and discover for yourself.

Subscribe Now

30-day free trial. Register in 60 seconds.

Related Solutions

  1. DirectX Draw Question - ?
    I use DirectX Draw in normal cooperative level mode and I need to blit off-screen surfaces onto primary. My off-screen surfaces are 8-bit palettized image data (with same palette as primary surface if video mode is in 8-bit palette). What I want to know is if the primary surf...
  2. Drawing Text with DirectX
    Hi, I would like to know what I would need to do to map ttf's to be able to draw them as graphics in DirectX, I really don't want to get the DC and use textout or drawtext, because I don't want to lose the speed benefits of DirectX. Basically, I am currently working on a stu...
  3. DirectX Help!
    Alright....What I need is a really fast way to place pixels on the screen using DirectX. (Windowed or Fullscreen) And I mean as fast as humanly possible. Any means possible is ok, as long as it compiles under my copy of Visual C++ 6.0 It would also be totally helpful...

Free Tech Articles

  1. WARNING: 5 Reasons why you should NEVER fix a computer for free.
    It is in our nature to love the puzzle. We are obsessed. The lot of us. We love puzzles. We love the challenge. We thrive on finding the answer. We hate disarray. It bothers us deep in our soul. W...
  2. SCCM OSD Basic troubleshooting
    SCCM 2007 OSD is a fantastic way to deploy operating systems, however, like most things SCCM issues can sometimes be difficult to resolve due to the sheer volume of logs to sift through and the dispe...
  3. Migrate Small Business Server 2003 to Exchange 2010 and Windows 2008 R2
    This guide is intended to provide step by step instructions on how to migrate from Small Business Server 2003 to Windows 2008 R2 with Exchange 2010. For this migration to work you will need the fo...
  4. Create a Win7 Gadget
    This article shows you how to create a simple "Gadget" -- a sort of mini-application supported by Windows 7 and Vista. Gadgets can be dropped anywhere on the desktop to provide instant information, ...
  5. Outlook continually prompting for username and password
    There have been a lot of questions recently regarding Outlook prompting for a username and password whilst using Exchange 2007. There are a few reasons why this would happen and I will try to cover t...
  6. Backup Exchange 2010 Information Store using Windows Backup
    There seems to be quite a lot of confusion around the ability to backup Exchange 2010 using the built in Windows Backup feature. This stems from the omission of this feature prior to Exchange 2007 s...

Cloud Class Webinars

  1. Avoiding Bugs in Microsoft Access
    Alison Balter takes and in-depth look at avoiding bugs in Access. In this webinar you will learn about using the immediate window to debug your applications, invoking the debugger, using breakpoints to troubleshoot, stepping through code, setting the next statement to execute, ...
  2. Top 10 Best New Features in Visio 2010
    Scott Helmers gives live demonstrations of the top 10 new features in Visio 2010. This webinar will teach you how to create compelling diagrams by adding shapes to the page with a single click, linking the shapes in a diagram to data in Excel (or SQL Server, or SharePoint), ...
  3. IT Consultant Business Secrets Revealed
    Michael Munger, Experts Exchange tech pro and IT consultant, pulls back the curtain on his very successful businesses and answers question on every IT consultant and business owner should know about. He shares secrets on what he did to solve the 5 most common problems in IT, ...
  4. Disaster Recovery and Business Continuity
    Quest CTO, Mike Billon, gives an overview of the steps involved in building a dunamic disaster recovery plan. Through case studies and an examination of software/hardware tooles for monitoring and testing, you'll gain a better understandin of where you are, where you want ...
  5. Organize Your Visio Diagrams with Containers and Lists
    Scott Helmers uses cross functional flowcharts, wireframe diagrams, data graphic legends and seating charts to teach you: how to ustilize all three new structured diagram components in Visio 2010, the best practices for organizeing shapes in previous version of Visio, how to organize ...
  6. How to Us Objects, Properties, Events and Methods in Microsoft Access
    Alison Dalter gives an in-depbth look at objects, properties, events and methods in Microsoft Access. In this webinar you will learn about using the object browser, referring to objects, working with properties and methods, working with object variables, understanding the ...

Join the Community

Give a Little. Get a Lot.

Join the community of experts here and help other tech pros by answering question in your area of expertise. You can earn FREE access to all Experts Exchange's premium features and resources.

Join the Community

Answers

 

by: thegilbPosted on 2007-05-22 at 05:33:54ID: 19133288

Some of your pseudo-code is a little bit sketchy on the details which are important but there are a few things to think about:

1.) Memory; It's faster to keep your data in a surface than in an array. If you can keep your data in the surface then do that instead of just using it as an intermediate data storage.

2.) Alignment; It looks as though you are working with a surface which has a linear memory layout. On some hardware it is faster to create a non-linear surface (One where the pitch and stride need to be used to plot a pixel). Other than that working with 128 bytes is a nice round number (In binary :-)

3.) Hardware support for 4bpp display mode is uncommon (8bpp is the norm) then you may find you need to convert your data to the correct format (8bpp) before flipping. You may find this to be quite costly and it would be faster to store your data in 8bpp (1byte = 1pixel) but just use the first 16 palette entries.

4.) CPU cycles are a valuable resource on a PPC device, beware of CPU wastage. Also embedded chipsets tend not to be as advanced as desktop counterparts so old-skool optimisation tricks will work well to save those cycles on these devices.

Hope that helps! Good luck!

 

by: EvlichPosted on 2007-05-22 at 06:34:16ID: 19133724

So what is the fastest way to get data computed on the CPU into a surface? I feel that pixel plotting would be too slow so I figured I could speed things up if I computed pixels for an entire line (possibly more) before writing the results to video memory.

I was thinking that there would be something Blt() which would be able to transfer memory from a buffer in main memory to video memory but I've been unable to find something like that without first going through some HBITMAP or something like that.

Many thanks.

 

by: thegilbPosted on 2007-05-22 at 06:43:08ID: 19133809

You're right, pixel plotting would be slow. I dont know the specifics because you haven't told me the processor but I can imagine that the hit would be fairly severe. You should be able to use a memcopy to copy a line from system to video memory. Once you lock the surface and get a pointer to the first pixel. If you have a contiguous surface then you could memcopy the whole block over in one call which would probably be your fastest option - though referring to point 1 in my previous email it might be faster to work with the video memory directly depending on the specific bus speeds of the target device.

 

by: joachimcPosted on 2007-05-31 at 01:39:14ID: 19186310

I would recommend to look at the solutions or maybe even use a pocket pc library like
http://www.codeproject.com/ce/cegraph.asp

Good luck

 

by: thegilbPosted on 2007-05-31 at 01:52:38ID: 19186364

To be honest, as long as you're using GAPI then there's really no need to use someone else's library ... Personally, I wouldn't trust someone else to write really well optimised code, but then that's me for you :-) You can download just GAPI here:
http://www.microsoft.com/downloads/details.aspx?familyid=D9879B0E-4EF1-4049-9C61-E758933D84C4&displaylang=en

GAPI lets you access video memory directly, so you have system level access to video memory. To be honest my previous posts did assume you were already using this library though from what it sounds like you might not have been!

I hope this helps :-)

20120131-EE-VQP-002

3 Ways to Join

30-Day Free Trial

The Experts

98% positive feedback on 31,087 answers since March 2000. angeliii is a Microsoft Most Valuable Professional for his work with MS SQL Server & Develoment.

He has also proven his knowledge of Visual Basic Programming, PHP Scripting and Oracle Databases.

The Experts

97% positive feedback on 10,752 answers since July 2000. lrmoore has more than 18 years experience in the networking industry.

The six-time Mircosoft MVPs specialties include firewalls, virtual private networking, and network management.

Testimonials

"...and excellent source for support... Kind of like having your very own IT dept." Electriciansnet

Testimonials

"I was apprehensive at signing up at first. However... it has already made my life as an IT administrator much easier." JaCrews

Testimonials

"WOW! You guys have great, active, and knowledgeable people on here." moore50

Business Clients

Business Clients

In the Press

"If you’ve got a question... Experts Exchange can supply an answer.”

In the Press

"...an invaluable aid for both IT professionals and those who require tech support."

In the Press

"where IT professionals provide quick answers on just about any topic"

Business Account Plans

Loading Advertisement...