| Re: IDL and C- [message #39510 is a reply to message #39413] |
Thu, 20 May 2004 14:49  |
JD Smith
Messages: 850
Registered: December 1999
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Senior Member |
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On Thu, 20 May 2004 13:50:43 -0700, Ryan Smith wrote:
> M. Katz-
>
> Thanks a bunch for your response. I tried the code and ran into more
> issues. Upon using the call_external it simply converts the image
> variable back to a long since IDL does its variable type declarations
> on the fly. I then tried the following code:
> image = ptr_new(bytarr(call_external("C:\Users\11ryan\CIDLFinal\testDLL\Debug\testDLL.dll ","testDLL")))
> window, xsize=640, ysize=480 ;--- open a window for display
> help, image
> tvscl, *image
>
> And the help, image says that it is a pointer, but when trying to
> display it i get an error saying TVSCL: Width and Height must be less
> than 32000. It looks as if it is trying to take the value and use it
> as a dimension instead. Any more advice on what I could try? thanks
> again for all the help-
>
> -Ryan
>
> MKatz843@onebox.com (M. Katz) wrote in message news:<4a097d6a.0405192255.693cd62b@posting.google.com>...
>> This is just a guess, but you might try the following.
>>
>> ;--- declare image as a pointer to an array of byte type
>> image = ptr_new(bytarr(640,480))
>> image = call_external("C:\11ryan\temp\Debug\testDLL.dll","testDLL ")
>> window, xsize=640, ysize=480 ;--- open a window for display
>> tvscl, *image ;--- scale and display the contents of the image pointer
>>
>> after the call_external, you might also issue
>> print, image
>> If it returns something like this <PtrHeapVar1> then it's certainly a pointer.
>> M. Katz
You can't just return a raw character pointer from C and expect IDL to
convert it into an IDL array variable. The traditional way to do this
is first make an array in IDL, pass it by reference to the function
via call_external, and copy the camera data over to it before
returning. Something like:
image=bytarr(1024,1024)
ret = call_external("C:\11ryan\temp\Debug\testDLL.dll","testDLL ",image)
and in the C code:
int _blah _blah newtestDLL(int argc, void *argv[]) {
char *buffer,*out;
int i;
/* Grab buffer from the camera */
...
/* Copy to output array */
out=(char *)argv[0]; /* This points to the IDL image variable's data */
for(i=0;i<1024*1024;i++) out[i]=buffer[i];
return 1;
}
Note that IDL pointers and C pointers are completely different beasts
which share almost nothing in common (IDL's could more properly have
been called "references").
JD
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