Reading brightness value from a specific point


    Apr 08 2008 | 4:12 pm
    Hello.
    I just started to learn jitter, and I have a couple of questions.
    I want to read brightness value from a specific point and control the brightness of other clips with this value. Is it possible? Actually, I want two points from a clip and control two other clips.
    And one more thing is that I want to capture 720 480 anamorphic DV and do something with jitter and project it in 720 480 anamorphic.
    I changed aspect ratio in compression settings in jit.qt.grab, but I don't know how to change the jit.pwindow or jit.window.
    I hope someone would help me. Thank you :)
    eejin

    • Apr 08 2008 | 5:28 pm
      > I want to read brightness value from a specific point and control the brightness of other clips with this value. Is it possible? Actually, I want two points from a clip and control two other clips.
      do you want the relative brightness of a clip at a particular point in time, or the brightness of one pixel of a clip?
      if it's the former, take a look at the second output of jit.3m, as well jit.histogram.
      if it's the latter, the getcell message to jit.matrix should do the trick.
      to control brightness, look at jit.brcosa or jit.scalebias. if you're feeling randy, might be time to take a look at slab processing. make sure you've done all the tutorials first.
      > And one more thing is that I want to capture 720 480 anamorphic DV and do something with jitter and project it in 720 480 anamorphic.
      > I changed aspect ratio in compression settings in jit.qt.grab, but I don't know how to change the jit.pwindow or jit.window.
      to size a jit.window either provide the width and height as arguments after the name argument, or send it the size message. jit.pwindow requires a right-click, get-info to set the size. all of this is covered in the respective help files.
      -rob
    • Apr 09 2008 | 4:42 am
      Thank you for your help.
      I meant a particular pixel on a clip.
      I'll try the way you suggested.
      As for the second question, I know how to size a jit.window, but the problem is that I can't change the aspect ratio. This makes my image look stretched vertically. because I'm using 16:9 DV camera. Anybody can help me?
    • Apr 09 2008 | 9:05 pm
      just size the movie, grab or window object to the correct aspect
      ratio by writing in the correct dimensions... etc
      max v2;
      On Apr 9, 2008, at 12:42 AM, Lee-jin Kim wrote:
      >
      > Thank you for your help.
      > I meant a particular pixel on a clip.
      > I'll try the way you suggested.
      >
      > As for the second question, I know how to size a jit.window, but
      > the problem is that I can't change the aspect ratio. This makes my
      > image look stretched vertically. because I'm using 16:9 DV camera.
      > Anybody can help me?
      >
      >
    • Apr 11 2008 | 5:58 am
      Thanks for your help.
      I made 16:9 window. But still what confuse me is when I make the jit. window to fullscreen, it just change the shape to fill the entire screen no matter what the size of the jit. window is.
      Actually, my notebook has 16:9 monitor, so now Even though my jit.window is 4:3, it displays the image 16:9 when it goes to fullscreen. But as I'm planing to display the final though a projector, I'm worried what it would look like.
      I'll use the projector as the second monitor. So the patch on the notebook monitor and the output image on the projector screen...
      Please give me any advice. And I'm sorry I didn't test it with a projector yet.
    • Apr 11 2008 | 6:45 am
      Hello there,
      I managed to read the alpha and RGB values from a particular point on a clip. But I'm yet confused how to apply these to control other clips
      I understand that jit brcosa controls brightness, but what calculation with 4 values would do the best results cause jit.brcosa require one value?
      As I'm writing this question, I'm realizing what I want to do is realtime color correction, not only the brightness control.
      Is it too much or too heavy?
      here, I have my patch.
      If I could add the remainder which I take A from B back to the values of the whole pixels on the clip A. I guess it would do.
      Is there an object like that? jit. scalebias does this? I read the help menu but I got a vague understanding of it
    • Apr 11 2008 | 5:37 pm
      Quote: eejin wrote on Thu, 10 April 2008 23:58
      ----------------------------------------------------
      > Thanks for your help.
      > I made 16:9 window. But still what confuse me is when I make the jit. window to fullscreen, it just change the shape to fill the entire screen no matter what the size of the jit. window is.
      >
      > Actually, my notebook has 16:9 monitor, so now Even though my jit.window is 4:3, it displays the image 16:9 when it goes to fullscreen. But as I'm planing to display the final though a projector, I'm worried what it would look like.
      you have to scale the vidoeplane based on your aspect ratio. then just set the erase_color of the gl.render to black, which will give you the black bars at the top and bottom.
      a potentially easier method is to export your movies in the aspect ratio of the projector, but pre-matted at 16:9.
    • Apr 11 2008 | 5:42 pm
      Quote: eejin wrote on Fri, 11 April 2008 00:45
      ----------------------------------------------------
      > I managed to read the alpha and RGB values from a particular point on a clip. But I'm yet confused how to apply these to control other clips
      >
      > I understand that jit brcosa controls brightness, but what calculation with 4 values would do the best results cause jit.brcosa require one value?
      totally depends on what you want to do. adding the values or averaging them are possibilities of how to turn 4 values into 1.
      > As I'm writing this question, I'm realizing what I want to do is realtime color correction, not only the brightness control.
      > Is it too much or too heavy?
      not too heavy for the computer, but pretty heavy for a beginner. your best bet is to find vade's v001 shader pack, as that is one the best possible ways to do realtime color correction with jitter.
    • Apr 14 2008 | 9:30 am
      Thank you for your help.
      But I don't understand many things. I'm sorry I'm such a beginner.
      As for the 16:9 issue, I better use gl.render, because I'm using live camera, and I can't prematte the source.
      What do you mean by "scale videoplane" Do you mean sizing the jit.window. I made the jit.window like
      jit.window eejin @size 720 405
      720 405 is 16:9
      And what is "set the erase_color of the gl.render to blacks"?
      I made jit.gl.render, but I don't know even where to put this? before jit.window or after it?
      and I don't know how to set the attribute. Is it like
      jit.gl.render @erase_color black????
      Could please explain more step by step, please?
      In addition, what is vade's v001 shader pack?
      Does this work like a plug in in other programs like after effect ? Where can I find it?
    • Apr 14 2008 | 12:55 pm
      Hello, rob
      Could you reply to one more question?
      When you use "getcell", you input "getcell X Y" to jit.matix,
      and then if you print from the right outlet of the matrix, you can see the info like "cell 0 0 val 255 31 190 33"
      And from that point, how can you put the last 4 list(alpha, R,G,B) into the number box, so you can start to do some calculation?
      I'm reading tutorials by my self, but it's pretty hard for me.
      Thank you in advance.
      eejin
    • Apr 14 2008 | 5:46 pm
      i'll do my best to answer your questions, but you really need to do the tutorials (at least the ones specific to what you're trying to achieve), study the help files, and study the html reference files.
      > What do you mean by "scale videoplane" Do you mean sizing the jit.window. I made the jit.window like
      16/9 = 1.77
      jit.gl.videoplane @scale 1.77 1. 1.
      you can then use the z position value to move zoom it in and out, or play with the transform_reset attribute.
      > And what is "set the erase_color of the gl.render to blacks"?
      > I made jit.gl.render, but I don't know even where to put this? before jit.window or after it?
      > and I don't know how to set the attribute. Is it like
      jit.gl.render @erase_color 0. 0. 0. 1.
      > In addition, what is vade's v001 shader pack?
      > Does this work like a plug in in other programs like after effect ? Where can I find it?
      http://001.vade.info/?page_id=20
      but i wouldn't recommend looking at those until you understand the basics.
      > When you use "getcell", you input "getcell X Y" to jit.matix,
      > and then if you print from the right outlet of the matrix, you can see the info like "cell 0 0 val 255 31 190 33"
      > And from that point, how can you put the last 4 list(alpha, R,G,B) into the number box, so you can start to do some calculation?
      however you want. add them up and scale the value to whatever it needs to be, is one possible easy method.
      3*255=765 (ignoring the alpha value here)
      so send the summed output to [scale 0 765 0. 1.] to scale it from 0. to 1. a very crude measure of brightness.
    • Apr 15 2008 | 11:54 am
      Thank you, rob
      Of course I'll read the tutorials later, but for now I have a show coming and I don't have much time to read one by one.
      Actually, I'm trying to find what chapters I should look at, and to read those chapters first, but I can't even figure out what those are yet.
      I have several problems unsolved. Maybe I'll give up couple of things. However I really need to achieve 16:9 image.
      So, could you please take a look at my patch and let me know where I should put the jit.gl.videoplane and jit.gl.render?
      Thank you so much in advance. :) Maybe I'm asking you too much.
    • Apr 15 2008 | 3:29 pm
    • Apr 16 2008 | 12:46 pm
      Thank you, rob
      I really appreciate it. I'm so relieved now. I could check other things for my show.
      I'll keep in mind that your advice, I'll read by my self later.
      Thank you again.
      eejin
    • Apr 26 2008 | 5:08 pm
      How are you, rob
      I came back asking your help.
      I'm trying to make my patch able to record, the patch that you helped me with.
      I attached jit.qt.record to the videoplane outlet. Is it wrong?
      It asked me filename but, didn't make even a file.
      And I made message box like "write name 29.97 dvntsc lossless"
      Is it ok? I'm using qmetro 20.
      I'm looking forward your reply.
      eejin
    • Apr 26 2008 | 7:07 pm
      > I attached jit.qt.record to the videoplane outlet. Is it wrong?
      yes.
      look at examples/jitter-examples/render/jit.gl.render-tomatrix.pat
      also check out the iShowU app for better performance.
      and make sure you search the forum. there are several posts in the last year addressing this.
    • May 02 2008 | 4:24 pm
      How are you, rob
      I opened my show a couple of days ago. It doesn't seem very successful but it's still meaningful experience for me.
      I thank you very much for your help.
      I plan to study max/msp/jitter during this summer, realizing this is very useful. So I'll come back here soon.
      Thanks again.
      eejin