impReadRow(3) Impressario impReadRow(3)NAME
impReadRow, impReadRowB, impWriteRow, impWriteRowB - read/write SGI Image
Format files
SYNOPSIS
#include <imp.h>
int impReadRow(IMPImage *image, short *buffer,
ushort_t row, ushort_t channel);
int impReadRowB(IMPImage *image, uchar_t *buffer,
ushort_t row, ushort_t channel);
int impWriteRow(IMPImage *image, short *buffer,
ushort_t row, ushort_t channel);
int impWriteRowB(IMPImage *image, uchar_t *buffer,
ushort_t row, ushort_t channel);
DESCRIPTION
impReadRow and impReadRowB each read a row of image data from the
specified channel of an SGI Image Format file. impReadRow stores the row
data in an array of short integers and therefore can read image data that
is either one or two bytes per pixel per channel in width. impReadRowB
stores the data in a character array and can only handle image data that
is one byte per pixel per channel wide. If impReadRowB is called to read
image data that is two bytes per pixel per channel, an error condition is
reported.
impWriteRow and impWriteRowB each write a row of image data to the
specified channel of an SGI Image file. impWriteRow writes one or two
byte per pixel per channel image row data. impWriteRowB writes only one
byte per pixel data. It is an error to use impWriteRowB to write to
images that expect two byte per pixel per channel data.
The functions take the following parameters.
image Pointer to an IMPImage structure returned by a call to
impOpen or impOpenFd.
buffer Caller allocated buffer containing the data to write to or
to be filled with the data read from the image. The amount
of storage allocated for the buffer should be
impXSize(image) * sizeof(short) if impReadRow or
impWriteRow functions are used and impXSize(image) if
impReadRowB or impWriteRowB are used.
row The image row to read. Rows are numbered from 0 through
impYSize(image) - 1.
Page 1
impReadRow(3) Impressario impReadRow(3)
channel The image channel to read. Channels are numbered from 0
through impNumChannels(image) - 1.
RETURN VALUE
If execution was successful, all functions return the number of pixels
(not bytes) read or written. If an execution error occurred, -1 is
returned and IMPerrno is set.
EXECUTION ERROR CODES
In addition to the system error codes defined in errno.h, the following
libimp specific error codes may be returned.
impWriteRow and impWriteRowB will fail under the following circumstances.
IMP_ERR_WRITEFLAG Attempt to write to an image file not opened for
writing.
IMP_ERR_BADBPP Unsupported bytes per pixel value. Refer to
imp.h for supported BPP values.
IMP_ERR_BADIMAGE Unrecognized image type. Refer to imp.h for
supported image types.
IMP_ERR_SHORTWRITE A complete row of data could not be written.
impReadRow and impReadRowB will fail under the following circumstances.
IMP_ERR_READFLAG Attempt to read from an image file not opened
for reading.
IMP_ERR_BADBPP Unsupported bytes per pixel value. Refer to
imp.h for supported BPP values.
IMP_ERR_BADIMAGE Unrecognized image type. Refer to imp.h for
supported image types.
IMP_ERR_SHORTREAD The amount of data read was less than the amount
expected based on the image size.
NOTE
It is the caller's responsibility to allocate enough buffer storage for
image row data.
SEE ALSOlibimp(3), impOpen(3)
Page 2
