Read/WritePixel Rgb Conversion

BlitzMax Forums/BlitzMax Programming/Read/WritePixel Rgb Conversion

AntonyWells

(Posted 2005) [#1]

Anyone know how to convert read/writepixel rgb values to seperate r,g,b values(In the range of 0-255) and back?

Here's what I have presently. GetRGB appears to work, but genRGb is (bleep)ed up.

	Function GenRgb( red,green,blue,alpha  )
Local rgb = ((alpha & $ff) Shl 24) | ((red & $ff) Shl 16) | (( green & $ff) Shl 8) | blue & $ff
		Return rgb
		
	End Function
	
	Function GetRGB(argb:Int,a Var,r Var, g Var, b Var)
		a=(argb Shr 24) & $ff
		r=(argb Shr 16) & $ff
		g=(argb Shr 8) & $ff
		b=argb & $ff
	End Function

Does the internal format of the pixel require further pixel conversion?

Why is this not in the docs? <Insert Rant>

tonyg

(Posted 2005) [#2]

Isn't it...

	Function GenRgb( red,green,blue,alpha=255  )
RGB = (alpha Shl 24) | (Red Shl 16) | (Green Shl 8) | Blue 
		Return rgb
		
	End Function

Example...

	Function GenRgb( red,green,blue,alpha=255  )
RGB = (alpha Shl 24) | (Red Shl 16) | (Green Shl 8) | Blue 
		Return rgb
		
	End Function
	
	Function GetRGB(argb:Int,a Var,r Var, g Var, b Var)
	a=(argb Shr 24) & $ff
	r=(argb Shr 16) & $ff
	g=(argb Shr 8) & $ff
	b=argb & $ff
End Function

Global alpha:Int,red:Int,green:Int,blue:Int

GetRGB($ff00ff00,alpha,red,green,blue)
Print alpha + " " + red + " " + green + " " + Blue
my_rgb=genrgb(red, green, blue, alpha)
GETRGB(my_rgb,alpha, red, green, blue)
Print alpha + " " + red + " " + green + " " + Blue

AntonyWells

(Posted 2005) [#3]

Thanks. Read pixel was still pretty shaky,
But I found a cool way of bypassing any of that.

P:Byte Ptr = Pixels.PixelPtr( x,y)

Red = P[2]
Green = p[1]
Blue = p[0]
Alpha = p[3]

But I have to use genRgb to encode it back..for some ..odd reason.