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Texture help

Blitz3D Forums/Blitz3D Beginners Area/Texture help

Blacky(Posted 2007) [#1]
I will use a simply 64,64 .bmp Image and make fast a copy of this image in the half colour values as the original is.

Can anybody help me, i use ReadPixelFast and WritePixelFast. How i can read the colour values of the Pixels and change them??

thx for help
Blacky


Dreamora(Posted 2007) [#2]
oldCol = ReadPixelFast
newcol = 0
for i = 0 to 2
val = ((oldcol shr 2^(i +3) ) and $FF) shr 1 ; shr 1 = /2
newcol = newcol + (val shl 2^(i +3) )
next
WritePixelFast newcol ...


Blacky(Posted 2007) [#3]
Use any image


; Load and draw an image on to the screen - can be anything

pic=LoadImage("test.bmp")
DrawImage pic,0,0



; Initialise an array big enough to fit all the color information of the screen
Dim pix(GraphicsWidth(),GraphicsHeight())

; Lock buffer before using ReadPixelFast
LockBuffer
;



; Use ReadPixel to get all the color information of the screen
For y=0 To GraphicsHeight()-1
For x=0 To GraphicsWidth()-1

pix(x,y)=ReadPixelFast(x,y)

Next
Next

; Lock buffer after using ReadPixelFast
UnlockBuffer



; Lock buffer before using WritePixelFast
LockBuffer

; Use WritePixel to redraw the screen using the color information we got earlier
For y=0 To GraphicsHeight()-1
For x=0 To GraphicsWidth()-1
WritePixelFast x,y,pix(x,y)
Next
Next

; Unlock buffer after using WritePixelFast
UnlockBuffer


WaitKey()


Dreamora(Posted 2007) [#4]
; Load and draw an image on to the screen - can be anything

pic=LoadImage("test.bmp")
DrawImage pic,0,0



; Initialise an array big enough to fit all the color information of the screen
Dim pix(GraphicsWidth(),GraphicsHeight())

; Lock buffer before using ReadPixelFast
LockBuffer
;



; Use ReadPixel to get all the color information of the screen
For y=0 To GraphicsHeight()-1
  For x=0 To GraphicsWidth()-1
    pix(x,y)= ReadPixelFast(x,y)
  Next
Next

; Lock buffer after using ReadPixelFast
UnlockBuffer



; Lock buffer before using WritePixelFast
LockBuffer

; Use WritePixel to redraw the screen using the color information we got earlier
For y=0 To GraphicsHeight()-1
  For x=0 To GraphicsWidth()-1
    newCol = 0
    for i = 0 to 2
      newCol = newCol +(( ( (pix(x,y) shr 2^(i +3) ) and $FF ) shr 1 ) shl 2^(i +3)  )
    next
    WritePixelFast x,y, newCol
  Next
Next

; Unlock buffer after using WritePixelFast
UnlockBuffer


WaitKey()


As shown in my code above already


Blacky(Posted 2007) [#5]
many thx for help Dreamora, but if you look at the image after is dark blue allways and its not like a shadow of the pic with the half brightness.

What is wrong here?

i have enclosed a code who do this well but its very very slow.

; GetColor Example

Graphics 1280,1024
SetBuffer BackBuffer()

pic=LoadImage("C:\Programme\Blitz3D\Samples\Blitz 3D Samples\1\Pics\Rüstung\test.bmp")
DrawImage pic,0,0

Dim pix(1200,1200,2)

For y=0 To 250
For x=0 To 250

GetColor(x,y)
pix(y,x,0) = ColorRed()
pix(y,x,1) = ColorGreen()
pix(y,x,2) = ColorBlue()

Next
Next



For y = 0 To 250
For x = 0 To 250
Color pix(y,x,0)/2,pix(y,x,1)/2,pix(y,x,2)/2 : Plot 0+x,0+y
Next
Next
Flip
While Not KeyHit(1)
Wend


Dreamora(Posted 2007) [#6]
Was an error in my code. Retry now should work.


Blacky(Posted 2007) [#7]
Sorry i have tried your code, but is the same as before.

Look at my code with the slow getcolor() it will do fine.

Something must be wrong, maybe you have done a mistake.


Dreamora(Posted 2007) [#8]
stupid me, copied the wrong thing over.
now it works


Blacky(Posted 2007) [#9]
yes its works now. First of all many thx for the fast help.

My last questions to understand the code. Can you explain me a little bit the formular u used

That i can understand what goes on


Dreamora(Posted 2007) [#10]
shr will shift the bits of the color ( stored as RGB in an image)
Each color component has a length of 8 Bit
After you shift it, you need to cut out only the color of interest, this is done by "and $FF", this will make anything but the last byte (8Bit) 0

The SHR 1 actually is just a different way to write / 2 (int)

The SHL afterwards just puts the before modified bits back in the correct position of the Int that represents the color


2^(3+i) : 2^3 = 8, the (3+i) above there is the same as (i*8) straight there so you potentially could toy with that directly. could potentially even be faster *forgot that Blitz3D is faster at multiplication than ^ with 3 and higher for the potence*