simple math doesn't work - GameCreators Forum

Author

Message

mr Handy

18

Years of Service

User Offline

Joined: 7th Sep 2007

Location: out of TGC

Posted: 29th May 2010 22:46

Link

hi! just wanted to make code, that coverts rgb photo to 512 colors (8 values per channel, 8*8*8=512)
and this simple math code doesn't work!
the result is more than 20000 colors

what is wrong?

p.s. use my code with any colorfull photo or picture.

+ Code Snippet

Sw=640
Sh=480
set display mode Sw,Sh,32,1
set window on
set window size Sw,Sh
sync on : sync rate 0

load image "1.jpg",1

repeat
paste image 1,0,0
if inkey$()="q"
lock pixels
for fy = 0 to 480
for fx = 0 to 640

c=point(fx,fy)
r=(rgbr(c)/32)*32
g=(rgbg(c)/32)*32
b=(rgbb(c)/32)*32
dot fx,fy,rgb(r,g,b)
next fx
next fy
unlock pixels
endif
sync
until spacekey()=1

Back to top

Profile PM

Phaelax

DBPro Master

23

Years of Service

User Offline

Joined: 16th Apr 2003

Location: Metropia

Posted: 29th May 2010 23:01

Link

your math makes no sense. You divide by 32 only to multiply by 32. Why are you dividing the color components by 32?

"Any sufficiently advanced technology is indistinguishable from magic" ~ Arthur C. Clarke

Back to top

Profile PM Email Website

Sven B

21

Years of Service

User Offline

Joined: 5th Jan 2005

Location: Belgium

Posted: 29th May 2010 23:47 Edited at: 29th May 2010 23:47

Link

mrHandy,

there's nothing wrong with your code, you're just pasting the old image over it every loop so you can't see the result.

Cheers!
Sven B

Back to top

Profile PM Email

mr Handy

18

Years of Service

User Offline

Joined: 7th Sep 2007

Location: out of TGC

Posted: 30th May 2010 10:08 Edited at: 30th May 2010 10:13

Link

@Sven B
There was inkey$ command for displaying result
@Phaelax
Now you will see the result of expression e=(100/32)*32
In DBP, variables are as integer by default.

I have modidfied the code for you two:

+ Code Snippet

Sw=640
Sh=480
set display mode Sw,Sh,32,1
set window on
set window size Sw,Sh
sync on : sync rate 0

load image "1.jpg",1

repeat
paste image 1,0,0
lock pixels
for fy = 0 to 480
for fx = 0 to 640

c=point(fx,fy)
r=(rgbr(c)/32)*32
g=(rgbg(c)/32)*32
b=(rgbb(c)/32)*32
dot fx,fy,rgb(r,g,b) `this line is pain
                     `dot sometimes draw colors that can't be calculated by previous math!
                     `like e=... below is 100!
next fx
next fy
unlock pixels

e=(100/32)*32:text 0,0,str$(e) `for Phaelax

sync
until spacekey()=1

Back to top

Profile PM

Latch

20

Years of Service

User Offline

Joined: 23rd Jul 2006

Location:

Posted: 30th May 2010 10:46 Edited at: 30th May 2010 10:50

Link

@mrHandy
I don't think your math approach is quite right. If you are trying to limit the number of colors to 512, then I think you'll have to do a 32 bit to 9 bit conversion - ( or 24 or 16 to 9 bit).

The red value would have to be within 111000000 = 448
the green value would have to be within 111000 = 56
and the blue value would have to be within 111 = 7

I'm typing as I'm thinking so I'm not sure how accurate the following formulas are but I think the conversion from a 24 bit rgb value would be

r = (rgbr(color) * 448) / 255
g = (rgbg(color) * 56) / 255
b = (rgbb(color) * 7) / 255

9bitcolor= r || g || b

The final color will have a maximum value of 512, I'm not sure if that's exactly what you are after.

Enjoy your day.

Back to top

Profile PM

mr Handy

18

Years of Service

User Offline

Joined: 7th Sep 2007

Location: out of TGC

Posted: 30th May 2010 11:02 Edited at: 30th May 2010 11:03

Link

well, your math result is red-black picture with 8000 colors.

Back to top

Profile PM

Latch

20

Years of Service

User Offline

Joined: 23rd Jul 2006

Location:

Posted: 30th May 2010 12:07 Edited at: 30th May 2010 12:15

Link

Quote: "well, your math result is red-black picture with 8000 colors."

Well, since the max number of colors should be 512 where the max value is 511, you'd have to convert the 9bit values back to 24 bit. And I can't see how there could possibly be 8000 colors as there are only 8 possible colors for any of the the 3 bit values.

For example, if your 24 bit color was pure white, rgb(255,255,255), then the 9bit value should be

r=(255 * 448) / 255 = 448 = 111000000
g=(255 * 56) / 255 = 56 = 111000
b=(255 * 7) / 255 = 7 = 111

r || g || b = 111111111 = 511

Perhaps it's not your goal to store the color values in a 9 bit value (you'd need a 9 bit system to display them)

You can convert them back to 24 bit before you display them (there will still only be 512 possible colors) if 9bitcolor=511 :

r = (255 * (9bitcolor && 448) ) / 448 = (255 * 448) / 448 = 255
g = (255 * (9bitcolor && 56) ) / 56 = (255 * 56) / 56 = 255
b = (255 * (9bitcolor && 7) ) / 7 = (255 * 7) / 7 = 255

You'd have to do similar conversions for 32 bit or 16 bit. A 32 bit value might be storing an alpha channel, so you might use a 10 bit value where bit 10 is on if there is an alpha channel and the other 9 bits store the 512 colors.

The approach I'm suggesting is reducing a higher bit depth color value to a lower color bit depth value - saving space for storage but losing color information. If you just want to store 8 values of each channel then just divide each channel by 8 and multiply it by 8

r=(rgbr(color)/8)*8
g=(rgbg(color)/8)*8
b=(rgbb(color)/8)*8

newcolor=rgb(r,g,b)

What does DarkBASIC Pro return for RGB() ? Is it a 32 bit value or a 24 bit value?

How about RGBR() > that must just return the red component.

I'm basing my answer on a 24 bit color value.

Enjoy your day.

Back to top

Profile PM

Lost in Thought

22

Years of Service

User Offline

Joined: 4th Feb 2004

Location: U.S.A. : Douglas, Georgia

Posted: 30th May 2010 12:41

Link

I'm agreeing with Phaelax. If you take a number and divide it by 32 and then multiply it by 32 ... then it's gonna be the same.

"e=(100/32)*32:text 0,0,str$(e) `for Phaelax"

e should be 100 0_o. I neglect to see the purpose in this at all really. I've never heard of 4 bit graphics. But if you want to adjust the scale so each pixel will scale down to from 0-256 to 0-8 then you just need to divide each channel by 32. I don't have DBP installed on this machine yet ... but wouldn't this work:

+ Code Snippet

Sw=640
Sh=480
set display mode Sw,Sh,32,1
set window on
set window size Sw,Sh
sync on : sync rate 0

load image "1.jpg",1

repeat
paste image 1,0,0
lock pixels
for fy = 0 to 480
for fx = 0 to 640

c=point(fx,fy)
r=rgbr(c)/32
g=rgbg(c)/32
b=rgbb(c)/32
dot fx,fy,rgb(r,g,b)

next fx
next fy
unlock pixels

sync
until spacekey()=1

You will notice though the picture won't look anything alike. Because you can't even begin to accurately show a 32 bit picture in 4 bit graphics. You'd have to come up with your own table as they did with even 16 bit graphics. Even then you'll be dissappointed mostly. 0_o

Back to top

Profile PM Email

mr Handy

18

Years of Service

User Offline

Joined: 7th Sep 2007

Location: out of TGC

Posted: 30th May 2010 14:02 Edited at: 30th May 2010 14:07

Link

@Latch
My goal is to make gif converter.
DBP returns color component as 0-255 value.

Quote: "If you just want to store 8 values of each channel then just divide each channel by 8 and multiply it by 8"

but it doesn't work!
(245/8)*8=240? yes! and no - there is 241 or 239 values! where did they come from!?
p.s. irfanview can calculate total number of unique colors in image - so any gif has 256 color but my pictures >9000!
@Lost in Thought
e=96

Back to top

Profile PM

Green Gandalf

VIP Member

21

Years of Service

User Offline

Joined: 3rd Jan 2005

Playing: Malevolence:Sword of Ahkranox, Skyrim, Civ6.

Posted: 30th May 2010 14:27

Link

mrHandy

Where do you get your figure of 20000 colours that you mention in your first post?

Why do you think your code doesn't work?

Lost in Thought and Phaelax

You both seem to have forgotten that DBPro performs "integer division" on integers - mrHandy's code is a simple way of converting the range 0, 1, ..., 255 to the range 0, 32, 64, ..., 224. Just try it.

The following simple variant of mrHandy's code illustrates the idea (don't forget to press q to see the result):

+ Code Snippet

Sw=640
Sh=480
set display mode Sw,Sh,32,1
set window on
set window size Sw,Sh
sync on : sync rate 0

create bitmap 1, 640, 480
box 0, 0, 640, 480, rgb(255, 0, 0), rgb(0, 255, 0), rgb(0, 0, 255), rgb(255, 255, 255)
get image 1, 0, 0, 640, 480, 1

set current bitmap 0

repeat
paste image 1,0,0
if inkey$()="q"
lock pixels
for fy = 0 to 480
for fx = 0 to 640

c=point(fx,fy)
r=(rgbr(c)/32)*32
g=(rgbg(c)/32)*32
b=(rgbb(c)/32)*32
dot fx,fy,rgb(r,g,b)
next fx
next fy
unlock pixels
endif
sync
until spacekey()=1

Back to top

Profile PM Email

Sven B

21

Years of Service

User Offline

Joined: 5th Jan 2005

Location: Belgium

Posted: 30th May 2010 19:41 Edited at: 30th May 2010 20:55

Link

Quote: "@Sven B
There was inkey$ command for displaying result"

You're right. Sorry I quickly pressed q and didn't realize I had to hold it...

Still. Your code works fine to me:

Not pressing q:

Pressing q:

Looks like worse quality to me...

[edit] It was a little hard to see, so I halved the size again ((comp/64)*64 instead of 32):

Your first code where I changed 32 -> 64:

+ Code Snippet

Sw=640
Sh=480
set display mode Sw,Sh,32,1
set window on
set window size Sw,Sh
sync on : sync rate 0
load image "box_uv.bmp",1

repeat
paste image 1,0,0
if inkey$()="q"
lock pixels
for fy = 0 to 480
for fx = 0 to 640

c=point(fx,fy)
r=(rgbr(c)/64)*64
g=(rgbg(c)/64)*64
b=(rgbb(c)/64)*64
dot fx,fy,rgb(r,g,b)
next fx
next fy
unlock pixels
endif
sync
until spacekey()=1

Also, the same can be achieved bitwise:

+ Code Snippet

r = rgbr(col) >> 5 : `2^5 = 32
g = rgbg(col) >> 5
b = rgbb(col) >> 5
dot fx, fy, rgb(r << 5, g << 5, b << 5)

Cheers!
Sven B

Back to top

Profile PM Email

Kevin Picone

23

Years of Service

User Offline

Joined: 27th Aug 2002

Location: Australia

Posted: 30th May 2010 20:14

Link

mrHandy,

If all you want to do is remove the lower bits from the channels, then just mask them off..

+ Code Snippet


 ; original 32 bit colour	
  ThisRgb=$ffffff
 
 ; mask to remove bottom 5 bits from each of  R,G,B channels
  Mask=$00e0e0e0    

 ; apply mask to remove lower bits from each channel
  C=ThisRGB and Mask  ;  Remove   

 ; Show 9 bit RGB colour in 32bit format
  print bin$(c)
 
 Sync
 waitkey

New PlayBasic Learning Edition Released 24th April 2010

Back to top

Profile PM Website

mr Handy

18

Years of Service

User Offline

Joined: 7th Sep 2007

Location: out of TGC

Posted: 30th May 2010 21:07

Link

Thanks for advices, guys!
Umm... it figures out, that my code was correct...
This is black magic!

If I copy screen (using "prt scr" button) and paste it to irfanview™, then screenshot will be... antialiased! (over 9000 colors, up to 32000)
If I make screenshot using fraps™ (saving as .bmp), it will have correct amount of colors!
Wtf with "prt scr"?

Back to top

Profile PM

Sorry your browser is not supported!

DarkBASIC Professional Discussion / simple math doesn't work