postage stamp coordinates are off for megacam spliced images

[bills]

The command

ppstamp out -file 870505p.fits -skycenter 1:16:32.948 8:23:25.65 -pixrange 200 200

should generate a postage stamp with an object that looks like a galaxy
at the center.

Instead the object is 32 pixels left of center.

The image is extracted from a mosaic image created with pmChipMosaic

readout is from the mosaic

psImage *subsetImage = psImageSubset(readout->image, options->roi);

make a copy since we're going to change the image's internals
outReadout->image =psImageCopy(NULL, subsetImage, subsetImage->type.type);
P_PSIMAGE_SET_COL0(outReadout->image, 0);
P_PSIMAGE_SET_ROW0(outReadout->image, 0);

where options->roi is a region centered on the chip coordinates for the object.
Pixel (1943, 3251)

The problem is that the coordinate system changes in the process of mosaicking
the chip.

If the image is extracted using the readout for the original input image
instead of the mosaic, the correct pixels are extracted.

Looking at the mosaic image we find that it is has col0=row0=0 and
so is effectively shifted to the left as well.

32 pixels is size of the overscan region.

[jhoblitt]

has this been fixed?