BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  timage and Jpeg          BorlandTalk.com Forum Index -> Delphi Graphics View previous topic :: View next topic   Author Message Luke Guest Posted: Thu Jun 17, 2004 8:06 am    Post subject: timage and Jpeg Hi, I have a situation where I need to display an image in a TImage. It can be either bmp or Jpg format. Once the image is loaded, they user can then draw on the image. I have been able to get around the whole copying the Jpeg to the Canvas of the Timage and works fine. The problem is that if the jpeg is bigger than what the timage size is (the timage cant be set to Autosize either, must be fixed), I draw on it, and then save the changes, the image that I end up with is not the original size, but the size of the TImage component. Is there any way that when I save the changes to a the jpg, that the original size is not lost? Sample Code Loading the Image: procedure TForm1.Button1Click(Sender: TObject); var MyJPEG : TJPEGImage; MyBMP : TBitmap; begin MyJPEG := TJPEGImage.Create; MyJPEG.LoadFromFile('C:SamplePic.jpg'); MyBMP := TBitmap.Create; MyBMP.Width := MyJPEG.Width; MyBMP.Height := MyJPEG.Height; MyBMP.Canvas.StretchDraw(Rect(0,0,MYJpeg.Width, MYJpeg.Height), MyJPEG); image1.Stretch := false; image1.Canvas.StretchDraw(image1.ClientRect,MyBMP); image1.Stretch := true; MyBMP.Free; MyJPEG.Free; end; end; Sample Code Saving the changes: procedure TForm1.Button2Click(Sender: TObject); var MyJPEG : TJPEGImage; MyBMP : TBitmap; begin MyJPEG := TJPEGImage.Create; MyJPEG.Assign(image1.Picture.Bitmap); MyJPEG.Scale := jsFullSize; MyJPEG.SaveToFile('C:Changed.jpg'); MyJPEG.Free; end; Thanks for any help, Luke. Back to top Yannis Guest Posted: Thu Jun 17, 2004 8:34 am    Post subject: Re: timage and Jpeg "Luke" <johnsluk (AT) hotmail (DOT) com> wrote in news:40d150ee$1 (AT) newsgroups (DOT) borland.com: Quote: procedure TForm1.Button1Click(Sender: TObject); var MyJPEG : TJPEGImage; MyBMP : TBitmap; begin MyJPEG := TJPEGImage.Create; MyJPEG.LoadFromFile('C:SamplePic.jpg'); MyBMP := TBitmap.Create; MyBMP.Width := MyJPEG.Width; MyBMP.Height := MyJPEG.Height; MyBMP.Canvas.StretchDraw(Rect(0,0,MYJpeg.Width, MYJpeg.Height), MyJPEG); Up until here everything is OK but in the next three lines of code you have managed to destroy all the previus work. It is clear that you do not have a clear understanding of what TImage is and how it works, So here are some basics TImage is not a component which handles the image data it self it is a painter component for TGraphic descentants only. I mean that you use TImage with a Tgraphic in order to interact with the user screen, read mouse movement paint graphics etc. Every time you do a draw in a Timage this is been redirected to the TGraphic that this component owns, If it doesn't have any Tgraphic Component then it creates a TBitmap object and it gives to it the dimensions of it self and the color depth of the computer it is running on. In sort at this point in your software you just need to assign the TBitmap you have created to the Timage component and you will be ready to start working, something like Image1.picture.assign(MyBMP); This will place the newly created MyBMP as the default paint object of the Image1 control and this will also correct the problem with autosize you have. Quote: image1.Stretch := false; image1.Canvas.StretchDraw(image1.ClientRect,MyBMP); image1.Stretch := true; Quote: MyBMP.Free; I thing that the above line shoold be removed otherwise you will either end up with a Timage component with a wrong referense or you will force it to duplicate the existing (I'm not sure about this to much VB I guess) in any case this at least will make you loose time or at worst crash your program later on. Quote: MyJPEG.Free; end; end; Regards Yannis. Back to top Joris Van Damme Guest Posted: Thu Jun 17, 2004 9:27 am    Post subject: Re: timage and Jpeg "Yannis" <None (AT) Noware (DOT) non> wrote Quote: It is clear that you do not have a clear understanding of what TImage is and how it works, So here are some basics A good (I hope) explanation can be found here http://www.awaresystems.be/techtalks/003_graphic_picture_image.html It is now available in both English and Dutch. A French version will be added soon. Quote: MyBMP.Free; I thing that the above line shoold be removed otherwise you will either end up with a Timage component with a wrong referense or you will force it to duplicate the existing (I'm not sure about this to much VB I guess) in any case this at least will make you loose time or at worst crash your program later on. That is not correct. Not freeing the bitmap is a leak. The bitmap's ownership is *not* transfered in the previous lines. Quote: MyJPEG := TJPEGImage.Create; MyJPEG.LoadFromFile('C:SamplePic.jpg'); MyBMP := TBitmap.Create; MyBMP.Width := MyJPEG.Width; MyBMP.Height := MyJPEG.Height; MyBMP.Canvas.StretchDraw(Rect(0,0,MYJpeg.Width, MYJpeg.Height), MyJPEG); Assigning would be the proper way to do this (if it needs to be done, see below). Drawing, like you do here, involves duplicate memory, and duplicating content. Assigning involves merely incrementing a usage counter (untill the time that either copy is actually edited, a principle that is called copy-on-write). Quote: image1.Stretch := false; image1.Canvas.StretchDraw(image1.ClientRect,MyBMP); image1.Stretch := true; That's the third copy then, even if this copy is scaled down. Quote: MyJPEG := TJPEGImage.Create; MyJPEG.Assign(image1.Picture.Bitmap); Assigning is the proper thing to do. But of course, you're using image1.Picture.Bitmap, which is the scaled copy, so of course your resulting saved jpeg will be scaled. In my opinion, the usage of TImage here is incorrect. The proper way to do it would be to handle an off-screen bitmap, do your editing on that off-scre en bitmap, and use a paintbox or similar for UI feedback. That is a bit more elaborate, code-wise, off course. Things that come to mind that may be usefull are Nils's virtual scrollbox and DTPDocuments component. (www.simdesign.nl) Good luck! 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 Luke Guest Posted: Thu Jun 17, 2004 9:57 pm    Post subject: Re: timage and Jpeg "Yannis" <None (AT) Noware (DOT) non> wrote Quote: "Luke" <johnsluk (AT) hotmail (DOT) com> wrote in news:40d150ee$1 (AT) newsgroups (DOT) borland.com: Image1.picture.assign(MyBMP); This will place the newly created MyBMP as the default paint object of the Image1 control and this will also correct the problem with autosize you have. Regards Yannis. Thanks for your help, works fine now. Luke. Back to top Yannis Guest Posted: Fri Jun 18, 2004 7:45 am    Post subject: Re: timage and Jpeg "Joris Van Damme" <PleaseReplyTo (AT) TheGroupInstead (DOT) be> wrote in news:40d163a3 (AT) newsgroups (DOT) borland.com: Quote: http://www.awaresystems.be/techtalks/003_graphic_picture_image.html Nice explenations and clear enough I have one question though at the end of the page you are saying and I quote /Quote Now you see where the Assign comes in. Internally, these TJpegImage and TBitmap objects are supposed to maintain rasters with usage counters. The Assign statement, officially, copies the raster content of the jpeg object into the bmp object. Underneath, this does *not* involve creating a second raster and copying the pixel data, but boils down to sharing the raster object and incrementing its usage counter, eliminating the need for duplicating memory. Quote/ I was under the impression that the raster content was the same until on of the objects made a change on it which in this time it would duplicate the device and apply the change tot he new content. regards Yannis. Back to top Joris Van Damme Guest Posted: Fri Jun 18, 2004 8:29 am    Post subject: Re: timage and Jpeg "Yannis" <None (AT) Noware (DOT) non> wrote Quote: http://www.awaresystems.be/techtalks/003_graphic_picture_image.html Nice explenations and clear enough I have one question though Thank you! Quote: at the end of the page you are saying and I quote /Quote Now you see where the Assign comes in. Internally, these TJpegImage and TBitmap objects are supposed to maintain rasters with usage counters. The Assign statement, officially, copies the raster content of the jpeg object into the bmp object. Underneath, this does *not* involve creating a second raster and copying the pixel data, but boils down to sharing the raster object and incrementing its usage counter, eliminating the need for duplicating memory. Quote/ I was under the impression that the raster content was the same until on of the objects made a change on it which in this time it would duplicate the device and apply the change tot he new content. Yes, as far as I understand you, that is exactly what I meant with the above quoted paragraph. If that wasn't clear, please help me make it clearer. I'm very much open for all suggestions. 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 Gordon Whittam Guest Posted: Fri Jun 18, 2004 10:13 am    Post subject: Re: timage and Jpeg In article <40d2a7a9 (AT) newsgroups (DOT) borland.com>, Joris Van Damme wrote: Quote: I'm very much open for all suggestions. "A TPicture is a descendant of TGraphic. " It's a descendent of TPersistent. Gordon Back to top Joris Van Damme Guest Posted: Fri Jun 18, 2004 10:45 am    Post subject: Re: timage and Jpeg "Gordon Whittam" <gordon (AT) mgcsoft (DOT) com> wrote Quote: "A TPicture is a descendant of TGraphic. " It's a descendent of TPersistent. You are right. Mea culpa. I don't understand howcome I was convinced of this, obviously without ever checking. I will correct the text without delay. Many thanks for pointing this out! 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 Joris Van Damme Guest Posted: Fri Jun 18, 2004 10:58 am    Post subject: Re: timage and Jpeg "Joris Van Damme" <PleaseReplyTo (AT) TheGroupInstead (DOT) be> wrote Quote: ...will correct the text... Done (remember to hit reload/refresh if you're interested in viewing the changes, first couple of hours). Thanks again. 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 Yannis Guest Posted: Fri Jun 18, 2004 11:27 am    Post subject: Re: timage and Jpeg "Joris Van Damme" <PleaseReplyTo (AT) TheGroupInstead (DOT) be> wrote in news:40d2a7a9 (AT) newsgroups (DOT) borland.com: Quote: "Yannis" <None (AT) Noware (DOT) non> wrote in message news:Xns950C6DB5DD9A9NoneNowarenon (AT) 207 (DOT) 105.83.66... http://www.awaresystems.be/techtalks/003_graphic_picture_image.html Nice explenations and clear enough I have one question though Thank you! at the end of the page you are saying and I quote /Quote Now you see where the Assign comes in. Internally, these TJpegImage and TBitmap objects are supposed to maintain rasters with usage counters. The Assign statement, officially, copies the raster content of the jpeg object into the bmp object. Underneath, this does *not* involve creating a second raster and copying the pixel data, but boils down to sharing the raster object and incrementing its usage counter, eliminating the need for duplicating memory. Quote/ I was under the impression that the raster content was the same until on of the objects made a change on it which in this time it would duplicate the device and apply the change tot he new content. Yes, as far as I understand you, that is exactly what I meant with the above quoted paragraph. If that wasn't clear, please help me make it clearer. I'm very much open for all suggestions. I would have said it like this. The assign statement adds a referense (or a pointer )to the existing raster contents increasing a counter which shows how many objects have access to this contents and it doesn't copy its data. At least not until the first time one of the objects that referencing the same raster makes a change to the contents. This change will actualy force a copy of the raster's data to a new memory address decreasing the referense counter and then apply the change. This way I find to be more accurate because 1) It descripes the steps of an assign 2) It descripes the steps taken when a change is made. 3) The raster is not an object (which is implied in your text) just a type like a record. Regards Yannis. Back to top Joris Van Damme Guest Posted: Fri Jun 18, 2004 12:10 pm    Post subject: Re: timage and Jpeg Quote: I would have said it like this. The assign statement adds a referense (or a pointer )to the existing raster contents increasing a counter which shows how many objects have access to this contents and it doesn't copy its data. At least not until the first time one of the objects that referencing the same raster makes a change to the contents. This change will actualy force a copy of the raster's data to a new memory address decreasing the referense counter and then apply the change. There is most defenetly parts of this that I want to use. Thank you very much! Quote: This way I find to be more accurate because 1) It descripes the steps of an assign Agreed. Quote: 2) It descripes the steps taken when a change is made. Agreed. Quote: 3) The raster is not an object (which is implied in your text) just a type like a record. I don't enterely agree here. After all, it's the descendant object that is repsonsable for maintaining the raster, and it can choose any type of record or object or whatever structure it sees fit. (Which kind of steps on the point... Yes, a descendant could decide to build an actual real duplicate copy inside the Assign implementation... Sigh.) Plus, I feel the word 'object' can also be used in the very general sense of 'thingy'. Plus, this is not a text for the very advanced, and we are discussing a detail in a subsection in a relatively small introductary text. But thank you for pointing out the copy-on-write role of Assign can be explained more clearly. I'm defenetly going to use part of your contribution. Thanks! 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 Yannis Guest Posted: Fri Jun 18, 2004 12:22 pm    Post subject: Re: timage and Jpeg "Joris Van Damme" <PleaseReplyTo (AT) TheGroupInstead (DOT) be> wrote in news:40d2db3a (AT) newsgroups (DOT) borland.com: Quote: I don't enterely agree here. After all, it's the descendant object that is repsonsable for maintaining the raster, and it can choose any type of record or object or whatever structure it sees fit. (Which kind of steps on the point... Yes, a descendant could decide to build an actual real duplicate copy inside the Assign implementation... Sigh.) Plus, I feel the word 'object' can also be used in the very general sense of 'thingy'. Plus, this is not a text for the very advanced, and we are discussing a detail in a subsection in a relatively small introductary text. Neet picking I know but i have this thing to say the things exactly as I see/understand them and be as accurate as possible. In my defense though I have taken in to account only the TBitmap object which holds a windows Tbitmap as raster contents which is in fact just a record in memory. I agree that it does not worth the effort especially since this might change based on the implementation of the object. Quote: But thank you for pointing out the copy-on-write role of Assign can be explained more clearly. I'm defenetly going to use part of your contribution. Thanks! I'm honored thank you Regards Yannis. 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