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Midterm Exam 1 Review Fall 2003: Picture concepts

(Back to Fall2003 Midterm Review 1)

Answers? Comments? Comments on answers?

1. we cant distinquish between the red, green, and blue spots because our human eyes cant distinguish between such small parts of a pixel. Is this somewhat correct?
2. Luminance is our perception of how light and dark things are.
3. In trying to figure out this one, I found that for 8-bit color, you need 6,291,456 bytes compared to 614,400 bytes for a 1024x768 size image. This is 10.24 times more memory to be able to store the bigger size image.

you got 1 and 2. For 3, you do need 10.24 times more memory but how much is that? Angela Liang
5,677,056 more bits is what you're asking for right?
The numbers are good, but it's also good to recognize the multiplier. 10.24, huh? Guess what 2 raised to the 10th power is? Mark Guzdial
are you looking for anything additional to the above stated (i.e. any particular memory value) or is the above stated adequate?
does that mean you need 2 more bits of memory?
Can someone explain how you got number 3?
OK, im officially confused now, i thought #3 was:

(1024 x 768 x 3)-(320 x 240 x 3)=2,128,896 bytes or 17,031,168 bits

am i way off here? or right maybe?
You're right – I'm sorry. It's 5 Mb – it's the 2 Mb you list. Mark Guzdial
>>> print 1024*768*3
2359296
>>> print 320*240*3
230400
>>> print (1024*768*3)-(320*240*3)
2128896

So, confused. I thought you needed 8 bits per color component (rgb). The larger screen (1024x768) has (1024)(768) = 78432 pixels. 78432 pixels multiplied by (8)(3) is 18874368 bits. Same for the smaller picture. Find the difference. Am I completely off base?
I thought that 8 bit per RGB means 24 bit per pixel meaning 1024 x 768 x 24 , why is it just 1024 x 768 x 3?
1024x768 = 786,432 pixels in the monitor image
320x240 = 76,800 pixels in the cheap picture image
786,432 - 76,800 = 709,632 difference of pixels
8 (bits per color component) x 3(color components per pixel) = 24 bits per pixel
709,632 pixels x 24bits = 17,031,168 bits
17,031,168 / 8 (bits per byte) = 2,128,896 more bytes

is this answer ok?
each byte is 8 bits, so if you multiply it by an 8, you're calculating the bits not bytes. 3 is for the number of primary color, red, green, blue. So what i would do is to just multiply each area by 3 and subract the different; that would be number of bytes, then you could multiply it by 8 to find the difference in bits. Houman Khalili
Right – bits vs. bytes. Mark Guzdial


yes, so the example in the notes is wrong eh?
24 bit color -> 320x240 image -> 1,843,200 bytes?
Shouldnt it be 230,400 bytes? (area times 3 bytes per pixel)
ok i dont understand...there are not 3 bits per byte there are 8 bits per byte. why is my answer wrong?
now can i panic because i thought i knew this and i dont and test in 42 minutes? lol



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