BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Question about JPEG decoding          BorlandTalk.com Forum Index -> Delphi Graphics View previous topic :: View next topic   Author Message Erik Turner Guest Posted: Sat Jun 19, 2004 10:22 pm    Post subject: Question about JPEG decoding I have been playing around with developing a fast JPEG image file compare tool. I've pretty much decided on comparing 16x16x2bit grayscale "thumbnails" of the images. What I need to do is quickly create these 16x16x2bit grayscale thumbnails. My current code converts the JPEG file to a 24 bit TBitmap and then uses the ScanLine property to quickly access the memory buffer. For images in the 200KB-300KB range, I can achieve about 10-15 thumbnails a second. I would like to do better than this if possible. Several things that I've read indicate that the IJG library has been improved since Borland took a snapshot (I'm using Delphi 5.0). Does anyone know of an updated version of JPEG.PAS? Or a pascal interface unit to the jpeg62.dll library? Thanks, Erik Turner Back to top Joris Van Damme Guest Posted: Sat Jun 19, 2004 10:31 pm    Post subject: Re: Question about JPEG decoding "Erik Turner" <erik (AT) turner (DOT) org> wrote Quote: What I need to do is quickly create these 16x16x2bit grayscale thumbnails. My current code converts the JPEG file to a 24 bit TBitmap and then... If memory serves, the IJG code is able to decode directly to grayscale, and do that significantly faster compared to decoding to 24bit RGB (not even counting the speed benefits from not having to convert to grayscale afterwards). I'm not too sure though, I could be confusing with something else. Joris Van Damme [email]info (AT) awaresystems (DOT) be[/email] http://www.awaresystems.be Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html Back to top Erik Turner Guest Posted: Sat Jun 19, 2004 11:15 pm    Post subject: Re: Question about JPEG decoding You are correct. In fact, I set the GrayScale property just after I load the image and it does go faster. But it still produces a 32 bit/pixel TBitmap object. I still think it would be faster if the TBitmap wasn't involved at all. Erik Turner "Joris Van Damme" <PleaseReplyTo (AT) TheGroupInstead (DOT) be> wrote Quote: "Erik Turner" <erik (AT) turner (DOT) org> wrote in message news:40d4bcc3$1 (AT) newsgroups (DOT) borland.com... What I need to do is quickly create these 16x16x2bit grayscale thumbnails. My current code converts the JPEG file to a 24 bit TBitmap and then... If memory serves, the IJG code is able to decode directly to grayscale, and do that significantly faster compared to decoding to 24bit RGB (not even counting the speed benefits from not having to convert to grayscale afterwards). I'm not too sure though, I could be confusing with something else. Joris Van Damme [email]info (AT) awaresystems (DOT) be[/email] http://www.awaresystems.be Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html Back to top Nils Haeck Guest Posted: Sun Jun 20, 2004 8:14 pm    Post subject: Re: Question about JPEG decoding Do you also use the TJpeg.Scale = jsEighth? That's a much higher improvement than the grayscale thing. I use it in my similarity check software ABC-View Manager: http://www.abc-view.com/abcview.html Kind regards, Nils "Erik Turner" <erik (AT) spamless (DOT) turner.org> wrote Quote: You are correct. In fact, I set the GrayScale property just after I load the image and it does go faster. But it still produces a 32 bit/pixel TBitmap object. I still think it would be faster if the TBitmap wasn't involved at all. Erik Turner "Joris Van Damme" <PleaseReplyTo (AT) TheGroupInstead (DOT) be> wrote in message news:40d4be50 (AT) newsgroups (DOT) borland.com... "Erik Turner" <erik (AT) turner (DOT) org> wrote in message news:40d4bcc3$1 (AT) newsgroups (DOT) borland.com... What I need to do is quickly create these 16x16x2bit grayscale thumbnails. My current code converts the JPEG file to a 24 bit TBitmap and then... If memory serves, the IJG code is able to decode directly to grayscale, and do that significantly faster compared to decoding to 24bit RGB (not even counting the speed benefits from not having to convert to grayscale afterwards). I'm not too sure though, I could be confusing with something else. Joris Van Damme [email]info (AT) awaresystems (DOT) be[/email] http://www.awaresystems.be Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html Back to top Erik Turner Guest Posted: Mon Jun 21, 2004 12:08 am    Post subject: Re: Question about JPEG decoding I haven't tried the Scale property. I assumed that it would generate a bitmap that, when stretched to 16x16, would be different than if I had stretched the original image to 16x16. Is this not the case? I want to use a very coarse thumbnail to do image similarity calculations. It takes about 291 nsec to compare two 16x16x2bit thumbnails and produce the "difference" metric (2.4GHz P4). Now I'm more concerned with the time spent generating these coarse thumbnails. I believe (and haven't verified) that the TJpegImage class generates a full size grayscale bitmap and then StretchDraw's it to my 16x16 bitmap. Erik Turner BTW, I downloaded and installed your viewer and it's a pretty nice program. "Nils Haeck" <n.haeckno (AT) spamchello (DOT) nl> wrote Quote: Do you also use the TJpeg.Scale = jsEighth? That's a much higher improvement than the grayscale thing. I use it in my similarity check software ABC-View Manager: http://www.abc-view.com/abcview.html Kind regards, Nils "Erik Turner" <erik (AT) spamless (DOT) turner.org> wrote in message news:40d4c91a$1 (AT) newsgroups (DOT) borland.com... You are correct. In fact, I set the GrayScale property just after I load the image and it does go faster. But it still produces a 32 bit/pixel TBitmap object. I still think it would be faster if the TBitmap wasn't involved at all. Erik Turner Back to top Joris Van Damme Guest Posted: Mon Jun 21, 2004 1:04 pm    Post subject: Re: Question about JPEG decoding "Erik Turner" <erik (AT) spamless (DOT) turner.org> wrote Quote: I haven't tried the Scale property. I assumed that it would generate a bitmap that, when stretched to 16x16, would be different than if I had stretched the original image to 16x16. Is this not the case? Depends on what you call 'different'. The result of decoding to an 1/8 downsample is *not* the same as just leaving pixels. It ressemles much more a area averaging downsample. So I guess it may be suitable for your purposes. Joris Van Damme [email]info (AT) awaresystems (DOT) be[/email] http://www.awaresystems.be Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html 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.