BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Difference between bitmaps          BorlandTalk.com Forum Index -> Delphi Graphics View previous topic :: View next topic   Author Message Paul Guest Posted: Mon Nov 22, 2004 8:12 pm    Post subject: Difference between bitmaps Hi all, I am searching for a fast way to get the difference between two bitmaps. I have found the (free) TBitmap32 component, which should be much faster than the standard bitmap, but it's not easy to start with. Does anyone here know another fast method ? Paul Back to top Pavel Vymazal Guest Posted: Mon Nov 22, 2004 9:22 pm    Post subject: Re: Difference between bitmaps What do you mean by "difference"? A possible solution would be to draw one of the bitmaps using CopyRect with Mode set to COPY, then draw the second one over it with Mode set to XOR. This way, equal pixels would become BLACK, while differing pixels will become (RGB-wise) colored as the RGB difference between the two pixels. The question is if this kind of "difference information" is helpful. "Paul" <paul.blommaerts (AT) telenet (DOT) be> pí¹e v diskusním pøíspìvku news:41a2481e (AT) newsgroups (DOT) borland.com... Quote: Hi all, I am searching for a fast way to get the difference between two bitmaps. I have found the (free) TBitmap32 component, which should be much faster than the standard bitmap, but it's not easy to start with. Does anyone here know another fast method ? Paul Back to top Nils Haeck Guest Posted: Tue Nov 23, 2004 12:19 am    Post subject: Re: Difference between bitmaps Hello Paul, What kind of difference? Do you want to just flag pixels that are different (only even by one bit) or do you want some kind of quality factor, where 0 means no difference and the bigger the value the bigger the difference. In first case, you can work with any type of bitmap and simply compare pixels. If they're equal, you flag them (or increment a counter). In second case, easiest to do is to use RGB bitmaps, and take the absolute or square of pixel channel value differences. Quote: I am searching for a fast way to get the difference between two bitmaps. I have found the (free) TBitmap32 component, which should be much faster than the standard bitmap, Not neccesarily. But certainly true if you were planning to use the Pixels property. Here's some code for (standard) TBitmaps with PixelFormat = pf24bits. I just wrote it down without checking, so there might be errors: function BitmapDifference(BmpA, BmpB: TBitmap): double; var x, y: integer; P, Q: PByte; Diff: int64; begin if not assigned(BmpA) or not assigned(Bmp) or (BmpA.PixelFormat <> pf24bit) or (BmpB.PixelFormat <> pf24bit) or (BmpA.Width <> BmpB.Width) or (BmpA.Height <> BmpB.Height) or (BmpA.Width * BmpA.Height = 0) then raise Exception.Create('Cannot compare bitmaps'); Diff := 0; for y := 0 to BmpA.Height - 1 do begin P := BmpA.Scanline[y]; Q := BmpB.Scanline[y]; for x := 0 to BmpA.Width - 1 do begin Diff := Diff + Sqr(P^ - Q^); inc(P); inc(Q); Diff := Diff + Sqr(P^ - Q^); inc(P); inc(Q); Diff := Diff + Sqr(P^ - Q^); inc(P); inc(Q); end; end; Result := Sqrt(Diff / (BmpA.Width * BmpA.Height)); end; This outputs differences as mean euclidian distance in RGB space averaged over pixel count. Routine should be pretty fast. A point not touched by this is comparing bitmaps that are actually not aligned to each other, or different in scale or rotation. If you want to do that, you face a much more difficult problem, for which my company has a solution (demo available). Kind regards, Nils Haeck www.simdesign.nl "Paul" <paul.blommaerts (AT) telenet (DOT) be> wrote Quote: Hi all, I am searching for a fast way to get the difference between two bitmaps. I have found the (free) TBitmap32 component, which should be much faster than the standard bitmap, but it's not easy to start with. Does anyone here know another fast method ? Paul Back to top Paul Guest Posted: Tue Nov 23, 2004 5:35 pm    Post subject: Re: Difference between bitmaps Hi all, I am trying to send image-streams to a host over the internet. Instead of sending the complete bitmaps, I am searching for the fastest way to do this. The code I use takes a new snapshot ,compares it with the preveous image and inverts it. This way, I have the changes of the last snapshot inverted. The rest of the image is black. After compression, the inverted image wich contains all changed pixels is transferred to the host. I have already speeded up the compression part, but I find the ' graphics part ' too slow. The code I use now bmp:= TBitmap.Create; GetPic(bmp); dif:= TBitmap.Create; dif.Assign(bmp); R:= Tect(0, 0, dif.Width, dif.Height); dif.Canvas.CopyMode:= cmSrcInvert; dif.Canvas.CopyRect(R, curbmp.Canvas, R); //curbmp is the previous snapshot curbmp.Assign(bmp); curbmp.Dormant; curbmp.FreeImage; Paul Back to top Nils Haeck Guest Posted: Tue Nov 23, 2004 10:36 pm    Post subject: Re: Difference between bitmaps That shouldn't be so slow.. But make sure that you also time your GetPic() routine, perhaps that is the bottleneck. Also, make sure that all bitmaps use the same PixelFormat. What is your maximum achievable framerate? If you want to speed things up you could use device independent bitmaps and then use MMX to do the pixel diffing. Have a look at Graphics32 for low-level MMX examples. Kind regards, Nils Haeck www.simdesign.nl "Paul" <paul.blommaerts (AT) telenet (DOT) be> wrote Quote: Hi all, I am trying to send image-streams to a host over the internet. Instead of sending the complete bitmaps, I am searching for the fastest way to do this. The code I use takes a new snapshot ,compares it with the preveous image and inverts it. This way, I have the changes of the last snapshot inverted. The rest of the image is black. After compression, the inverted image wich contains all changed pixels is transferred to the host. I have already speeded up the compression part, but I find the ' graphics part ' too slow. The code I use now bmp:= TBitmap.Create; GetPic(bmp); dif:= TBitmap.Create; dif.Assign(bmp); R:= Tect(0, 0, dif.Width, dif.Height); dif.Canvas.CopyMode:= cmSrcInvert; dif.Canvas.CopyRect(R, curbmp.Canvas, R); //curbmp is the previous snapshot curbmp.Assign(bmp); curbmp.Dormant; curbmp.FreeImage; Paul Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> Delphi Graphics All times are GMT Page 1 of 1   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.