AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  points vs pixels.          AppletTalk.com Forum Index -> Java Help View previous topic :: View next topic   Author Message Roedy Green Guest Posted: Wed May 19, 2004 9:07 pm    Post subject: points vs pixels. If you were ever confused about points vs pixels and font sizes, there are two new pages in the Java glossary to help you. http://mindprod.com/jgloss/point.html and http://mindprod.com/fontshower.html -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. Back to top Luke Tulkas Guest Posted: Thu May 20, 2004 9:51 am    Post subject: Re: points vs pixels. "Roedy Green" <look-on (AT) mindprod (DOT) com.invalid> wrote Quote: If you were ever confused about points vs pixels and font sizes, there are two new pages in the Java glossary to help you. http://mindprod.com/jgloss/point.html and http://mindprod.com/fontshower.html Drawing (painting) to different graphical devices can present a problem if you do it the old way (using integer Points, Rectangles, Fonts, etc.). But... There are other ways of doing it. Using Graphics2D (float Points, Rectangles, etc.), FontRenderContexts and TextLayouts, AffineTransforms. A bit more complicated, but it works (behind the scenes) like a charm. Everywhere. You don't even have to know the difference between pixels and points and that they're not the same on all devices. Maybe you could mention that in your glossary, too. Back to top Tom Guest Posted: Thu May 20, 2004 1:10 pm    Post subject: Re: points vs pixels. Roedy Green <look-on (AT) mindprod (DOT) com.invalid> wrote Quote: If you were ever confused about points vs pixels and font sizes, there are two new pages in the Java glossary to help you. http://mindprod.com/jgloss/point.html and http://mindprod.com/fontshower.html Thanks for all you do Roedy. One FYI/nit. When I viewed the applet in Mozilla, the last button on the right was cut off. Thought you'd want to know. Back to top Roedy Green Guest Posted: Thu May 20, 2004 4:08 pm    Post subject: Re: points vs pixels. On 20 May 2004 06:10:16 -0700, [email]tom.cowdery (AT) bigfoot (DOT) com[/email] (Tom) wrote or quoted : Quote: One FYI/nit. When I viewed the applet in Mozilla, the last button on the right was cut off. Thought you'd want to know. I looked with Mozilla and all seemed ok. Which button are you referring to? -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. Back to top Roedy Green Guest Posted: Thu May 20, 2004 4:36 pm    Post subject: Re: points vs pixels. On Wed, 19 May 2004 23:21:55 GMT-5, [email]DaleKing (AT) newsrvr (DOT) tce.com[/email] (Dale King) wrote or quoted : Quote: The default device coordinate space is 72 units per inch which does not necessarily correspond to pixels. The user can then add an affine transform to create whatever coordinate system they like. I will add that. I'm using Graphic2D a lot myself lately. I guess when I do these essays I am thinking only about the newbie, and tend to forget about more advanced stuff. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. Back to top Roedy Green Guest Posted: Thu May 20, 2004 5:34 pm    Post subject: Re: points vs pixels. On Thu, 20 May 2004 16:36:37 GMT, Roedy Green <look-on (AT) mindprod (DOT) com.invalid> wrote or quoted : Quote: default device coordinate space is 72 units per inch which does not necessarily correspond to pixels. The user can then add an affine transform to create whatever coordinate system they like. I will add that. This is now done. The material was there before, it is just now I put more emphasis on it. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. Back to top Dale King Guest Posted: Tue May 25, 2004 3:12 pm    Post subject: Re: points vs pixels. "Roedy Green" <look-on (AT) mindprod (DOT) com.invalid> wrote Quote: On Thu, 20 May 2004 16:36:37 GMT, Roedy Green [email]look-on (AT) mindprod (DOT) com.inva[/email]lid> wrote or quoted : default device coordinate space is 72 units per inch which does not necessarily correspond to pixels. The user can then add an affine transform to create whatever coordinate system they like. I will add that. This is now done. The material was there before, it is just now I put more emphasis on it. You added very little emphasis on it. You add it as an afterthought as though it were extraneous information. I'm sorry to be so nit-picky and this is an advanced topic that requires a paradigm shift in your way of thinking. But I don't think it is best to teach newbies the flawed concept of thinking in pixels only to then have to have them unlearn it later. It is best to start them down the right path from the beginning. Issues: "The origin 0,0 is in the top left corner...not the bottom left where Descartes put it": Technically Descartes put it in the center. The notion of top and bottom corresponding to a particular direction for y is an arbitrary convention. "For Java units are integer pixels": That was true for Java 1.1 but not for Java2D, where they are neither integer nor pixels. "For mouse events, drawing geometric shapes, and placing Components with absolute co-ordinates in the null layout, the origin 0,0 is the upper left corner.": The issue is the upper left corner of what? The answer depends on the situation, but is usually the container of the component. "When you place an object on the screen, you specify the location of its upper left corner.": Not necessarily true in user coordinate space. "For GridBagLayouts the origin 0,0 is the upper left corner of the enclosing container": This is not a function of the layout but of the container. "drawRectangle and brothers deliberately draw rectangles one pixel taller and wider than requested": That is true, but in Java2D you use drawShape and have much greater control. You specify where the border of the shape is and the stroke that is drawn on top of that line such that typically you are specifying the center of the drawn outline. "Because co-ordinates are measured in hardware-dependent pixels, images generated by Java programs will be smaller when they are displayed on high resolution displays": Not in Java2D I could go on but, I think that is a representative sample. -- Dale King My Blog: http://nobleware.homedns.org/Blog Back to top Roedy Green Guest Posted: Tue May 25, 2004 5:04 pm    Post subject: Re: points vs pixels. On Tue, 25 May 2004 10:12:53 -0500, "Dale King" <KingD (AT) tmicha (DOT) net> wrote or quoted : Quote: You added very little emphasis on it. You add it as an afterthought as though it were extraneous information It is for newbies. They start with AWT which uses integer addressing. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. Back to top Roedy Green Guest Posted: Tue May 25, 2004 5:21 pm    Post subject: Re: points vs pixels. On Tue, 25 May 2004 17:04:12 GMT, Roedy Green <look-on (AT) mindprod (DOT) com.invalid> wrote or quoted : Quote: You added very little emphasis on it. You add it as an afterthought as though it were extraneous information It is for newbies. They start with AWT which uses integer addressing. All the textbooks talk about integer addressing. Integer addressing is what happens eventually after all the Graphic2D methods have done their thing. If you want fine control to the pixel, you need integer addressing. Throwing in AffineTransforms is too much complication for the newbie. I think he should start with integer pixels. It is roughly the same argument as to whether you should teach an assembler language before or after Java. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. Back to top Roedy Green Guest Posted: Tue Jun 01, 2004 5:03 pm    Post subject: Re: points vs pixels. On Tue, 1 Jun 2004 07:59:54 GMT-5, [email]DaleKing (AT) newsrvr (DOT) tce.com[/email] (Dale King) wrote or quoted : Quote: So instead we should throw in false information to trip him up later whenhe finds that information wasn't true? I presented no false information. I simply presented in it an different order. The reasons I presented pixel level graphics first include: 1. You can't even draw a line with AffineTransform. 2. You don't need to understand the mathematically daunting transform matrices. Many people are terrified of trig. 3. You don't need to pick a co-ordinate system. 4. Every pixel rendered can be explained. With AffineTransform, things are only roughly accurate, and all falls apart if you start drawing detail on the pixel level. 5. It is faster. 6. Historically it is what came first. 7. It is what the beginner text books teach. 8. It is what underpin AffineTransforms. I think strange Affine rounding behaviours will make much more sense after you have fooled around at the pixel level. Now cut this calumny out. We simply disagree. Stop accusing me of spreading false information. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. Back to top Roedy Green Guest Posted: Mon Jun 07, 2004 8:18 pm    Post subject: Re: points vs pixels. On Sun, 6 Jun 2004 10:35:45 GMT-5, [email]DaleKing (AT) newsrvr (DOT) tce.com[/email] (Dale King) wrote or quoted : Quote: They won't make any sense atall based on your entry, because you have not given any basis to understand anything about it. Whentheyencounter something like that they will be confused and your stated purpose at the beginning of this thread was to eliminate confusion. It is pretty obvious what happens when you work at the pixel level and see the rounding problem, the hanging extra line of pixels etc. All of this is muddied when you use a transform. It comes down to this, pixels are conceptually simpler. AffineTransforms are more generic. I think it is easier to start with pixels. They are more abstract. Abstract is what you want when you know what you are doing. When you are just figuring things out, abstractions just get in the way. You can at least draw lines without having to think of them as rectangles of sufficient thickness to actually appear. The other thing ironically some newbie COULD start with the AffineTransform entry rather than co-ordinate entry and do it your way anyway. You want something with as few bells and whistles as possible when you are getting started. AffineTransform has a ton of them. I was trained as a mathematician, so AffineTransform is not that daunting. I have done for pay coaching on it, and it really does seem to scare the hell out of people without a math background. The wording I use now in talking about co-ordinate systems is more waffly. Perhaps is won't grate you so much. I think we have both stated our opinions clearly and it is time to agree to disagree. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. Back to top Dale King Guest Posted: Sun Feb 05, 2006 5:29 pm    Post subject: Re: points vs pixels. Hello, Roedy Green ! You wrote: Quote: If you were ever confused about points vs pixels and font sizes, there are two new pages in the Java glossary to help you. Except that you are spreading the confusion. Your information there is sadly out of date. The idea that user coordinates are integer and correspond to pixels was true back in the days of JDK1.1, but with the advent of Java2D that is no longer true. The default device coordinate space is 72 units per inch which does not necessarily correspond to pixels. The user can then add an affine transform to create whatever coordinate system they like. -- Dale King My Blog: http://daleking.homedns.org/Blog Back to top Dale King Guest Posted: Sun Feb 05, 2006 5:35 pm    Post subject: Re: points vs pixels. Hello, Roedy Green ! You wrote: Quote: On Tue, 25 May 2004 10:12:53 -0500, "Dale King" [email]KingD (AT) tmicha (DOT) net[/email] wrote or quoted : You added very little emphasis on it. You add it as an afterthought as though it were extraneous information It is for newbies. I see nothing limiting the article to newbies. And I don't see how you are doing them any favors by teaching them erroneous information that they will have to unlearn later. Quote: They start with AWT which uses integer addressing. AWT can use affine transforms and Swing also uses integer coordinates. The issue isnot so much whether the coordinates are integers, but the notion that coordinate units are pixels. -- Dale King My Blog: http://daleking.homedns.org/Blog Back to top Dale King Guest Posted: Sun Feb 05, 2006 5:35 pm    Post subject: Re: points vs pixels. Hello, Roedy Green ! You wrote: Quote: On Tue, 25 May 2004 17:04:12 GMT, Roedy Green [email]look-on (AT) mindprod (DOT) com.inva[/email]lid> wrote or quoted : You added very little emphasis on it. You add it as an afterthought as though it were extraneous information It is for newbies. They start with AWT which uses integer addressing. All the textbooks talk about integer addressing. Integer addressing is what happens eventually after all the Graphic2D methods have done their thing. If you want fine control to the pixel, you need integer addressing. Unless you understand the rendering process you will not get rendering to the pixel. Coordinate units are not necessarily pixels. And in reality you should not be designing to the pixel, because it is inherently unportable. Devices have different resolutions. I see no reason to start a newbie down that flawed path. Quote: Throwing in AffineTransforms is too much complication for the newbie. So instead we should throw in false information to trip him up later whenhe finds that information wasn't true? I'm not saying that there needs to be great detail on AffineTransform but there at least should not be false information and there should probably be a general overview of the rendering process. At least if there is going to be gross oversimplifications then it should be qualified as such with pointers to the true information. Quote: I think he should start with integer pixels. Why shouldthe newbie be lied to? Quote: It is roughly the same argument as to whether you should teach an assembler language before or after Java. Not a valid comparison. Assembler is additonal information. Here we are talking about replacement of factual information with oversimplified falsehoods. -- Dale King My Blog: http://daleking.homedns.org/Blog Back to top Dale King Guest Posted: Sun Feb 05, 2006 5:39 pm    Post subject: Re: points vs pixels. Hello, Roedy Green ! You wrote: Quote: On Tue, 1 Jun 2004 07:59:54 GMT-5, [email]DaleKing (AT) newsrvr (DOT) tce.com[/email] (Dale King) wrote or quoted : So instead we should throw in false information to trip him up later whenhe finds that information wasn't true? I presented no false information. I simply presented in it an different order. You said that coordinate units are pixels, which is not necessarily true and is generally not true for rendering for printing. Quote: The reasons I presented pixel level graphics first include: 1. You can't even draw a line with AffineTransform. You can draw a Shape where the shape consists of one or more line segments. You have so much more control over rendering and it is much nicer than drawing lines because you can declare the shape in relative coordinates and draw it anywhere easily. Once you are familiar with it you would never go back to the lousy pre-Java2D system. Quote: 2. You don't need to understand the mathematically daunting transform matrices. Many people are terrified of trig. I wasn't recommending you go to that level of detail and you really don't need to understand trig to know what an AffineTransform does for you and to understand the rendering pipeline. Quote: 3. You don't need to pick a co-ordinate system. But itis nice to know that you can. Quote: 4. Every pixel rendered can be explained. With AffineTransform, things are only roughly accurate, and all falls apart if you start drawing detail on the pixel level. And that is part of my point, you really shouldn't be drawing on the pixel level it isn't portable. Quote: 5. It is faster. There is no difference in speed. The rendering pipeline is used in either case. Quote: 6. Historically it is what came first. Vector and Hashtable came before the collections API, but I don't recommend teaching them in place of the collections API. Instead you teach the collections API and they are a footnote in that discussion. Quote: 7. It is what the beginner text books teach. That's a pretty low standard Quote: 8. It is what underpin AffineTransforms. I think strange Affine rounding behaviours will make much more sense after you have fooled around at the pixel level. They won't make any sense atall based on your entry, because you have not given any basis to understand anything about it. Whentheyencounter something like that they will be confused and your stated purpose at the beginning of this thread was to eliminate confusion. Quote: Now cut this calumny out. We simply disagree. Stop accusing me of spreading false information. Coordinate units are not necessarily pixels. 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