MyBytePtr [ 1 ]

BlitzMax Forums/BlitzMax Programming/MyBytePtr [ 1 ]

beanage

(Posted 2009) [#1]

So, the title is self- explanatory ..

Now its actually the question, whether the pointer value requesting is 'just' syntactical sugar, or consequently usable -

e.g. you could do extraction of color parts from the pixel value like:

 Local MyPixelValue:Int = ReadPixel( .. )
Local MyPixelValuePtr :Byte Ptr = Varptr MyPixelValue
Local MyPixelR :Int = MyPixelValuePtr[ 0 ]
Local MyPixelG :Int = MyPixelValuePtr[ 1 ]
Local MyPixelB :Int = MyPixelValuePtr[ 2 ]

Opinions?

Czar Flavius

(Posted 2009) [#2]

Well it seems to compile and run on mine, with numbers coming out (can't be bothered to check if they're correct though).

Jesse

(Posted 2009) [#3]

it works but note that the way a 32 bit integer is stored is not the same way a byte is accessed.
try this code:

 
Local MyPixelValue:Int = $FF88BBCC ' this is format PF_RGBA8888
Local MyPixelValuePtr :Byte Ptr = Varptr MyPixelValue
Local MyPixelR :Int = MyPixelValuePtr[ 0 ]
Local MyPixelG :Int = MyPixelValuePtr[ 1 ]
Local MyPixelB :Int = MyPixelValuePtr[ 2 ]
Local MyPixelA :Int = MyPixelValuePtr[ 3 ]
Print Hex(MyPixelR)' this will return blue not red
Print Hex(MyPixelG)' this will return green
Print Hex(MyPixelB)' this will return red not blue
Print Hex(MyPixelA)' this will return alpha

you are going to have to adopt your code accordingly

_Skully

(Posted 2009) [#4]

Ya, you can do that.. Similar code has been posted before

beanage

(Posted 2009) [#5]

One more reason to love blitzmax. Thanks to you all for your answers.