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Newcomers DBPro Corner / Colour Values

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Libervurto
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Posted: 14th Feb 2013 05:07 Edited at: 15th Feb 2013 01:24
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Coming from DBC I'm used to colour values being calculated like so:
(red * 65536) + (green * 256) + blue
This seems to work for DBP but printing the colour value to screen gives a negative number! What the hell is going on?

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pcRaider
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Posted: 14th Feb 2013 05:18 Edited at: 14th Feb 2013 05:23
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do not negative number.

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Phaelax
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Posted: 14th Feb 2013 08:05
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You gotta make it a dword, not integer. Both 4 bytes, but the high bit for integers is used for sign. Dwords are unsigned and therefore hold higher values.

"You're all wrong. You're all idiots." ~Fluffy Rabbit
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Libervurto
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Posted: 14th Feb 2013 08:09
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Thanks guys, I probably should have guessed that since I do stuff like ink -1,0 for white ink.

^ That's what she said.
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Phaelax
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Posted: 14th Feb 2013 08:14
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Quote: " I do stuff like ink -1,0 for white ink"

I never thought about that before.

You can also use hex values just like web stuff.

ink 0xFF0000, 0

"You're all wrong. You're all idiots." ~Fluffy Rabbit
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TheComet
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Posted: 14th Feb 2013 10:17
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You should probably check this before blindly believing me, but I think bitwise operators might be faster than multiplications. If not, they are definitely more readable.

(red << 16) || (green << 8) || blue

TheComet

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Rudolpho
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Posted: 14th Feb 2013 17:11
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Don't forget col = alpha << 24 || red << 16 || green << 8 || blue.

Not supplying the alpha value will have it default to 0, thus making your colour completely transparent. To add to the confusion some functions only seem to use 24-bit colours and skip the alpha byte, while some others doesn't.


"Why do programmers get Halloween and Christmas mixed up?"
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Libervurto
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Posted: 14th Feb 2013 21:10
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Ah yeah I forgot DBP can do bit-shifting.

^ That's what she said.
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Phaelax
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Posted: 14th Feb 2013 23:55
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I think awhile back we tested the speed of using multiplication versus bit shifting, and for this particular example we didn't really see any difference.

Also, is there a reason you're not simply using RBG()?

"You're all wrong. You're all idiots." ~Fluffy Rabbit
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Libervurto
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Posted: 15th Feb 2013 00:38 Edited at: 15th Feb 2013 00:59
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@Phaelax
I am drawing sprites (my procedural spaceships) and was testing for colours >0 to avoid drawing the transparent parts of the image, that's how I stumbled on the negative values.

^ That's what she said.

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Rudolpho
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Posted: 15th Feb 2013 03:08
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Quote: "Also, is there a reason you're not simply using RBG()?"

I don't know how DBP implements bit shifting, but RGB, unless optimized and translated into something similar during compilation, will yield function calling overheads which you probably don't want if you're editing each pixel on a large bitmap etc.


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Phaelax
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Posted: 15th Feb 2013 05:55
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Good point.

"You're all wrong. You're all idiots." ~Fluffy Rabbit
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pcRaider
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Posted: 19th Feb 2013 08:48
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Quote: "
Don't forget col = alpha << 24 || red << 16 || green << 8 || blue.
"


It's a BOX command only.
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TheComet
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Posted: 19th Feb 2013 13:38
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@ pcRaider - I don't get how that's relevant.

TheComet

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"You're all wrong. You're all idiots." - Fluffy Rabbit
"Bottom line, people are retarded." - Fluffy Rabbit
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Phaelax
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Posted: 19th Feb 2013 17:41
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Only using color values in conjunction with the BOX command will make use of the alpha channel.

"You're all wrong. You're all idiots." ~Fluffy Rabbit
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