| cursor_image [message #25879] |
Thu, 26 July 2001 07:45  |
slashell
Messages: 2
Registered: June 2001
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Junior Member |
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IDL help for Cursor_image keyword says:
Specifies the cursor pattern. The value of this keyword must be a
16-line by 16-column bitmap, contained in a 16-element short integer
vector. The offset from the upper left pixel to the point that is
considered the hot spot can be provided via the CURSOR_XY keyword.
I assumed that each of the elements of the vector could be determined
by writing the decimal equivalent of a binary number where the binary
number specified which of the pixels in that row should be set and
which should not. I further assumed that the least significant bit
would be the rightmost bit:
32768,16384,8192,4096,2048,1024,512,256,128,64,32,16,8,4,2,1
Thus, to set only the third pixel from the left on a given row, one
would specify the number 8192 for that row.
What I seem to have discovered is that the order of the bits is:
512,1024,2048,4096,8192,16384,32768,1,2,4,8,16,32,64,128,256
Thus, to set only the third pixel from the left on a given row, one
would specify the number 2048 for that row.
Is this correct? If so, why?????????? This arrangement makes no
sense to me.
Looking for sense in a crazy software environment,
Sean
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| Re: cursor_image [message #25962 is a reply to message #25879] |
Fri, 27 July 2001 05:18  |
Alex Schuster
Messages: 124
Registered: February 1997
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Senior Member |
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Sean La Shell wrote:
> Specifies the cursor pattern. The value of this keyword must be a
> 16-line by 16-column bitmap, contained in a 16-element short integer
> vector. The offset from the upper left pixel to the point that is
> considered the hot spot can be provided via the CURSOR_XY keyword.
>
> I assumed that each of the elements of the vector could be determined
> by writing the decimal equivalent of a binary number where the binary
> number specified which of the pixels in that row should be set and
> which should not. I further assumed that the least significant bit
> would be the rightmost bit:
> 32768,16384,8192,4096,2048,1024,512,256,128,64,32,16,8,4,2,1
>
> Thus, to set only the third pixel from the left on a given row, one
> would specify the number 8192 for that row.
>
> What I seem to have discovered is that the order of the bits is:
> 512,1024,2048,4096,8192,16384,32768,1,2,4,8,16,32,64,128,256
>
> Thus, to set only the third pixel from the left on a given row, one
> would specify the number 2048 for that row.
>
> Is this correct? If so, why?????????? This arrangement makes no
> sense to me.
The two bytes the 16-bit integer consists of are swapped. This usually
comes from data being processed on machines with different endianess,
sometimes the hi-value bytes come first, sometimes it's the other way
around, depending on the CPU You can use the BYTEORDER procedure or the
SWAP_ENDIAN() function to change that.
Alex
--
Alex Schuster Wonko@planet-interkom.de
alex@pet.mpin-koeln.mpg.de
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