GDALSuggestedWarpOutput uses too much memory on large images

[warmerdam]

I have discovered that in GDAL 1.9 if you invoke GDALSuggestedWarpOutput() on an image that is large (say 1000000 by 1000000) then the working grid is allocated very large (at 1/50 resolution in both directions) - so several GB.

The memory use is an issue, but if the estimation needs to use grid oriented rather than edge oriented it also would presumably do way too much work.

This code is the issue:

#define N_PIXELSTEP 50
    int nSteps = (int) (double(MIN(nInYSize, nInXSize)) / N_PIXELSTEP + .5);
    if (nSteps < 20)
        nSteps = 20;

[warmerdam]

Fixed in trunk (r25707) and 1.9 (r25706) to limit each dimension to 100.