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Re: reading / writing the color of an absolute pixel (x,y) of the physical screen

From owl <owl@rooftop.invalid>
Newsgroups alt.os.linux
Subject Re: reading / writing the color of an absolute pixel (x,y) of the physical screen
Date 2019-06-27 13:53 +0000
Organization O.W.L.
Message-ID <da888q3q.t3qut3q@rooftop.invalid> (permalink)
References (6 earlier) <qevssk$l6u$3@dont-email.me> <s8z0b8803tag.au4@rooftop.invalid> <qf0fdj$6pp$2@dont-email.me> <szv803ga.3ghui@rooftop.invalid> <qf25lp$1mv$1@dont-email.me>

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Soviet_Mario <SovietMario@cccp.mir> wrote:
> On 27/06/19 01:05, owl wrote:
>> Soviet_Mario <SovietMario@cccp.mir> wrote:
>>> On 26/06/19 16:00, owl wrote:
>>>> Soviet_Mario <SovietMario@cccp.mir> wrote:
>>>>> On 26/06/19 14:35, owl wrote:
>>>>>> Soviet_Mario <SovietMario@cccp.mir> wrote:
>>>>>>> On 26/06/19 10:37, F. Russell wrote:
>>>>>>>> On Wed, 26 Jun 2019 01:13:47 +0200, Soviet_Mario wrote:
>>>>>>>>
>>>>>
>>>>> very kind ! I'll have a look if I don't get the native
>>>>> Gambas way to work
>>>>> Tnx
>>>>>
>>>>
>>>> xdotool helps a lot with x11 automation stuff:
>>>> This will give you color for a pixel at x y:
>>>> e.g. ./pixelcolor 100 300
>>>>
>>>> #!/bin/bash
>>>> (xdotool mousemove ${1} ${2}; xdotool click 1) |grabc
>>>>
>>>>
>>>> This will capture a rectangle x1 y1 x2 y2 to /tmp/out.png:
>>>> e.g. ./rectcapture 110 212 373 400
>>>>
>>>> #!/bin/bash
>>>> (xdotool mousemove ${1} ${2}
>>>> xdotool mousedown 1;
>>>> xdotool mousemove ${3} ${4}
>>>> xdotool mouseup 1) |scrot -s /tmp/out.png
>>>>    
>>>>
>>>
>>> I would prefer to avoid both "shelling" and inter-processes
>>> switching if not strictly inevitable and/or if done rarely
>>> at big chunks at a time.
>>> One thing is to just load a library once at startup and then
>>> call its APIs, another is using multiple times (millions of
>>> times) cli commands.
>>>
>> 
>> You said you're not doing video graphics, 
> 
> well, not in the sense to make animation or mass batch 
> processing, apply multiple effects or so to many pictures 
> ... but a reasonable speed is required.
> Say I want to mask and watermark a 2000x1000 pixel, it'd be 
> always 2000000 millions calls. An interprocess approach to a 
> console utility is out of question.
> I can't even use the high level gambas native functions on 
> bitmaps, I just used them once at load and once at transfer 
> of finished outcome
> 
>> so why would you need to
>> get a rectangle millions of times?  If you're wanting to get the
>> pixels individually, look at the grabc source code.
>> 
>> https://github.com/immunant/grabc/blob/master/grabc.c
> 
> Thanks .... anyway as I said elsewhere, I discovered a 
> "renamed" function called Desktop.Screenshot (native to 
> gambas) that is lightening and supports any rectangle of the 
> current screen).
> 
> Now i'm up to finding a way to also transfer the content to 
> a DrawingArea or other container. I find the approach 
> unfamiliar (and have to understand the difference of 
> management among "dynamic" graphics, which are implemented 
> via IMAGE object, and managed internally, and "static" 
> graphics, impl. via PICTURE object, and said to be 
> transfered to X server internal buffers : I have confused 
> ideas on this multiple layer approach and thus getting 
> strange results, like output that is permanent : can be 
> saved on files but do not show up anywhere, and output that 
> is visible but is not redrawn when a part of the window is 
> covered and re-exposed).
> 
> But I don't mean to annoy the NG with these problems, as are 
> no longer general linux-related.
> I had tried a wrong way to bypass "impasse" (and you all 
> gave kind advices).
> But I still have more general problem comprehension about 
> the whole graphics model of Gambas (which replicates 
> somewhat the philosophy of server X).
> 
> I didn't mean to submit general programming issues, I'm 
> often OT enough ! :)
> 

You might also consider looking into the perl Image::Imlib2
interface.  Reading all pixels from a screenshot of my desktop
(1600x900) took about 2.6 seconds:

anon@lowtide:~/code/imlib2$ time ./doit >data

real    0m2.580s
user    0m2.532s
sys     0m0.044s
anon@lowtide:~/code/imlib2$ wc -l data
1440000 data
anon@lowtide:~/code/imlib2$ head data
x,y: 0,0   r: 223 g: 111 b: 0 a: 255
x,y: 0,1   r: 192 g: 95 b: 0 a: 255
x,y: 0,2   r: 192 g: 95 b: 0 a: 255
x,y: 0,3   r: 192 g: 95 b: 0 a: 255
x,y: 0,4   r: 192 g: 95 b: 1 a: 255
x,y: 0,5   r: 192 g: 95 b: 1 a: 255
x,y: 0,6   r: 192 g: 95 b: 0 a: 255
x,y: 0,7   r: 192 g: 95 b: 0 a: 255
x,y: 0,8   r: 192 g: 95 b: 0 a: 255
x,y: 0,9   r: 192 g: 95 b: 0 a: 255
anon@lowtide:~/code/imlib2$ tail data
x,y: 1599,890   r: 157 g: 152 b: 149 a: 255
x,y: 1599,891   r: 156 g: 151 b: 148 a: 255
x,y: 1599,892   r: 156 g: 151 b: 147 a: 255
x,y: 1599,893   r: 155 g: 150 b: 146 a: 255
x,y: 1599,894   r: 156 g: 151 b: 148 a: 255
x,y: 1599,895   r: 155 g: 150 b: 147 a: 255
x,y: 1599,896   r: 156 g: 148 b: 146 a: 255
x,y: 1599,897   r: 157 g: 149 b: 147 a: 255
x,y: 1599,898   r: 157 g: 149 b: 147 a: 255
x,y: 1599,899   r: 156 g: 148 b: 146 a: 255
anon@lowtide:~/code/imlib2$ 

https://manpages.debian.org/stretch/libimage-imlib2-perl/Image::Imlib2.3pm.en.html

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Thread

reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-25 17:53 +0200
  Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Alfonso P Cutaway <dweed54@gmail.com> - 2019-06-25 16:01 +0000
    Re: reading / writing the color of an absolute pixel (x,y) of the physical screen "R.Wieser" <address@not.available> - 2019-06-25 19:03 +0200
      Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Alfonso P Cutaway <dweed54@gmail.com> - 2019-06-25 18:08 +0000
        Re: reading / writing the color of an absolute pixel (x,y) of the physical screen "R.Wieser" <address@not.available> - 2019-06-25 21:44 +0200
          Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Alfonso P Cutaway <dweed54@gmail.com> - 2019-06-26 00:37 +0000
            Re: reading / writing the color of an absolute pixel (x,y) of the physical screen "R.Wieser" <address@not.available> - 2019-06-26 10:50 +0200
              Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Alfonso P Cutaway <dweed54@gmail.com> - 2019-06-26 19:43 +0000
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen "Carlos E.R." <robin_listas@es.invalid> - 2019-06-26 22:37 +0200
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Alfonso P Cutaway <dweed54@gmail.com> - 2019-06-26 20:55 +0000
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen "Carlos E.R." <robin_listas@es.invalid> - 2019-06-26 23:29 +0200
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Aragorn <thorongil@telenet.be> - 2019-06-26 23:50 +0200
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Alfonso P Cutaway <dweed54@gmail.com> - 2019-06-26 22:50 +0000
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen DecadentLinuxUserNumeroUno@decadence.org - 2019-06-28 12:50 +0000
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen DecadentLinuxUserNumeroUno@decadence.org - 2019-06-28 12:56 +0000
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen "R.Wieser" <address@not.available> - 2019-06-27 11:10 +0200
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-27 12:39 +0200
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen "R.Wieser" <address@not.available> - 2019-06-27 14:43 +0200
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-27 15:57 +0200
        Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-26 01:03 +0200
          Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Alfonso P Cutaway <dweed54@gmail.com> - 2019-06-26 00:38 +0000
  Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Wildman <best_lay@yahoo.com> - 2019-06-25 11:18 -0500
    Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-26 01:02 +0200
      Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Aragorn <thorongil@telenet.be> - 2019-06-26 01:08 +0200
  Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Bit Twister <BitTwister@mouse-potato.com> - 2019-06-25 11:48 -0500
  Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Paul <nospam@needed.invalid> - 2019-06-25 16:14 -0400
    Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-26 01:13 +0200
      Re: reading / writing the color of an absolute pixel (x,y) of the physical screen "F. Russell" <fr@random.info> - 2019-06-26 08:37 +0000
        Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-26 12:29 +0200
          Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Bit Twister <BitTwister@mouse-potato.com> - 2019-06-26 06:55 -0500
          Re: reading / writing the color of an absolute pixel (x,y) of the physical screen "F. Russell" <frussell@random.info> - 2019-06-26 12:15 +0000
          Re: reading / writing the color of an absolute pixel (x,y) of the physical screen owl <owl@rooftop.invalid> - 2019-06-26 12:35 +0000
            Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-26 15:44 +0200
              Re: reading / writing the color of an absolute pixel (x,y) of the physical screen owl <owl@rooftop.invalid> - 2019-06-26 14:00 +0000
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-26 21:01 +0200
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen owl <owl@rooftop.invalid> - 2019-06-26 23:05 +0000
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-27 12:27 +0200
                Re: reading / writing the color of an absolute pixel (x,y) of the physical screen owl <owl@rooftop.invalid> - 2019-06-27 13:53 +0000
  Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Jasen Betts <jasen@xnet.co.nz> - 2019-06-26 10:13 +0000
  Re: reading / writing the color of an absolute pixel (x,y) of the physical screen Soviet_Mario <SovietMario@CCCP.MIR> - 2019-06-26 12:49 +0200

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