canvas

BlitzMax Forums/BlitzMax Programming/canvas

Cronos (Posted 2007) [#1]

how read pixel from canvas , speed code ??? Function GetPixel(x:Int, y:Int, r:Int Var, g:Int Var, b:Int Var) Local TempPixmap:TPixmap = GrabPixmap(x,y,1,1) Local TempPtr:Byte Ptr = TempPixmap.PixelPtr(0,0) r = TempPtr[2] g = TempPtr[1] b = TempPtr[0] End Function

N (Posted 2007) [#2]

Sorry, what?

Cronos (Posted 2007) [#3]

how read pixel fast from canvas ??

N (Posted 2007) [#4]

Last I checked, there was no way to read pixel data quickly from a canvas or graphics buffer.

ImaginaryHuman (Posted 2007) [#5]

For OpenGL at least I'd recommend you simply define an Integer and then pass the pointer to that integer as a parameter to glReadPixels() and read just 1 pixel, it will put the value into the integer. You have to set up the glreadpixels properly with a few other commands first. This should be faster than creating a new pixmap each time, converting the coordinates into an offset, reading into the memory (which uses glreadpixels internally for gl), and then extracting the components. You could also use a byte pointer pointing to the integer to extract.