Texture help

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

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 ...

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()

; 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

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

Was an error in my code. Retry now should work.

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.

stupid me, copied the wrong thing over.
now it works

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

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*