Get a valid rational choice value from a driver.
Declaration:
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AT_ERRCOUNT ACCUAPI IG_ISIS_choice_get_rational(
HISISDRV hDriver,
AT_MODE nTag,
WORD wIndex,
LPAT_ISIS_RAT lpValue
);
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Arguments:
| Name | Type | Description |
| hDriver | HISISDRV | The handle to the driver. |
| nTag | AT_MODE | The tag for which a valid rational value is being requested. |
| wIndex | WORD | An index to a particular element of the array of valid tag values. |
| lpValue | LPAT_ISIS_RAT | A pointer to a RAT buffer that will contain the result of IG_ISIS_choice_get_rational. |
Return Value:
Error count.
Supported Raster Image Formats:
This function does not process image pixels.
Example:
The following example first determines whether the choices of a rational value, IG_ISIS_TAG_XRESOLUTION, are implemented as a range or a list, then gets each value and prints it to the standard output:
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nErrCount = IG_ISIS_choice_get_flags(hDriver, IG_ISIS_TAG_XRESOLUTION, &lValue);
if (nErrCount != IGE_SUCCESS) return nErrCount;
/* If choices are stored as a range, get the low, high, and step: */
if (lValue & IG_ISIS_CONT_RANGE) {
nErrCount = IG_ISIS_choice_get_rational(hDriver, IG_ISIS_TAG_XRESOLUTION,
IG_ISIS_CHOICE_LOW, &ratResLo);
if (nErrCount != IGE_SUCCESS) return nErrCount;
nErrCount = IG_ISIS_choice_get_rational(hDriver, IG_ISIS_TAG_XRESOLUTION,
IG_ISIS_CHOICE_HIGH, &ratResHi);
if (nErrCount != IGE_SUCCESS) return nErrCount;
nErrCount = IG_ISIS_choice_get_rational(hDriver, IG_ISIS_TAG_XRESOLUTION,
IG_ISIS_CHOICE_STEP, &ratResStep);
if (nErrCount != IGE_SUCCESS) return nErrCount;
printf(" Range:\n %ld%ld - %ld%ld by %ld%ld\n",
ratResLo.Num, ratResLo.Denom,
ratResHi.Num, ratResHi.Denom,
ratResStep.Num, ratResStep.Denom);
}
/* If choices are stored as a list, get and print the entire list: */
if (lValue & IG_ISIS_CONT_LIST) {
nErrCount = IG_ISIS_choice_get_count(hDriver, IG_ISIS_TAG_XRESOLUTION, &wCount);
if (nErrCount != IGE_SUCCESS) return nErrCount;
printf(" Values:\n");
for (w=0; w < wCount; w++) {
nErrCount = IG_ISIS_choice_get_rational(hDriver, IG_ISIS_TAG_XRESOLUTION, w,
&ratRes);
if (nErrCount != IGE_SUCCESS) return nErrCount;
printf(" %3ld%ld" , ratRes.Num, ratRes.Denom);
if ((w%7) == 6 || (w == wCount-1))
printf("\n"); // seven per line
}
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Remarks:
The IG_ISIS_choice_get_rational function fills in lpValue with the value referenced by wIndex from tag nTag.
This function must be used only for tags which have a type of IG_ISIS_TAG_TYPE_RATIONAL. Use the IG_ISIS_tag_get_type function to determine the type of a tag.
The IG_ISIS_choice_get_count function can be used to determine the total number of legal values for a tag. wIndex must be at least 0 and at most the value returned by IG_ISIS_choice_get_count - 1. The constants IG_ISIS_CHOICE_LOW and IG_ISIS_CHOICE_HIGH can be used to retrieve the 0th and nth values of a list or range; however, keep in mind that a list must be sorted from low to high values for these constants to return the actual low and high values of the list. Also, IG_ISIS_CHOICE_STEP can be used if the flag IG_ISIS_CONT_RANGE is set. The value returned by IG_ISIS_choice_get_rational using a wIndex value of IG_ISIS_CHOICE_STEP is the difference between any two consecutive values.
The toolkit's RAT value consists of a signed 32-bit numerator (Num) and a signed 32-bit denominator (Denom), comprising a fractional value: The individual values of a AT_ISIS_RAT type can be accessed as conventional elements:
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ratValue.Num
ratValue.Denom
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