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Code briefing

The code provided merely performs a color conversion required to go from the input NTSC image to the output RGB image. The relevant streams of data are brought in using the in_luma, in_cr, in_cb odd and even streams

The odd, even is done because the input YcbCr data is interlaced and the different "color" components Y(luminance), Cr, and Cb are stored in different arrays, unlike RGB where the data is packed together for each pixel. Thus the streams are accessed inside the color_conv_image wrapper function. We then pass a line at a time to the color_conv component function which converts and flips one line at a time.

We will need to modify the code here, in color_conv to achieve your goals. The control surface will be a square block 100 by 100 pixels in the bottom left corner of the screen. The brightness will be calculated by summing all the R, G and B values of all the pixels in this portion of the screen. We then apply the tint effect as such:

  • if the total brightness is below a certain level 'X': use a red tint,
  • if the total brightness is above 'X' and below 'Y' : use a green tint,
  • if above 'Y' : use a blue tint

The tint has to be scaled too. For example, if brightness is less than X but close to it we need a high blue. But if it's closer to zero we need a darker blue and so on. The scaling need not be linear. In fact if you did the auto-contrast function you will have noticed that the floating point operations are expensive, they tend to slow the system. This is more so in the color case, as we have more data to scale. So try to use simple bit shifts to achieve the needed effect.

  • Right Shift : >>
  • Left Shift : <<
  • Masking : Use a single ampersand, so to extract the first red component: RGB[1] &amp; 0xF8

Tips and tricks

You're on your own now! But some things to remember and to watch out for are presented here, as well as ideas for improvement. Remember:

  • The input is two bytes per pixel. Keep the packed RGB format in mind.
  • Also we process one line at a time from top to bottom. We cannot go back to previous lines to change them. So we can only modify the tint of the screen below the control surface. What you could do however is keep global variables for the different scalings in main. Then pass these to color_conv by reference, and update it when converting colors. But perform the update after using the existing scale values to scale the screen region above the control surface. This will introduce a delay from scaling change to screen update. This can be solved by copying the entire input to memory before outputting it but this is quite expensive, and we'll deal with memory in the next section.
  • Be careful when performing masking, shifting and separting. Bring things down to least significant set of bits (within a byte) to simplify thinking of the scaling. Also be careful not to overlap masks, especially during shifting and adding

Here are a few recommendations:

  • Try to use the Y data passed to the color_con funtion to compute the brightness – much faster.
  • Also poke around and find out how to use the Cr, Cb data and scale those. It's far less expensive and may produce neater results.
  • If something doesn't work, think things through again. Or better still take a break and then come back to the problem.

Questions & Answers

do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Mueller Reply
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Source:  OpenStax, Ece 320 spring 2004. OpenStax CNX. Aug 24, 2004 Download for free at http://cnx.org/content/col10225/1.12
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