| Message ID | 20250428103604.151551-2-david.plowman@raspberrypi.com |
|---|---|
| State | New |
| Headers | show |
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| Related | show |
Hi David, On Mon, 28 Apr 2025 at 11:36, David Plowman <david.plowman@raspberrypi.com> wrote: > > The problem occurs when the calculation could lead to a final row (or > column) of grid squares with no pixels in them (and hence, NaNs). > > One specific case is a Pi 5 with an image width (or height) of 1364, > so that's 682 Bayer quads. To give 32 grid squares it was calculating > 22 quads per cell. However, 31 * 22 = 682 leaving nothing in the final > column. > > The fix is to do a rounding-down division by the number of cells minus > one, rather than a rounding-up division by the number of cells. This > turns the corner case from one where the final row/column has no > pixels to one where we don't quite cover the full image, which is how > we have to handle these cases. > > Signed-off-by: David Plowman <david.plowman@raspberrypi.com> Reviewed-by: Naushir Patuck <naush@raspberrypi.com> > --- > utils/raspberrypi/ctt/ctt_alsc.py | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/utils/raspberrypi/ctt/ctt_alsc.py b/utils/raspberrypi/ctt/ctt_alsc.py > index 1d94dfa5..f4fd09e3 100644 > --- a/utils/raspberrypi/ctt/ctt_alsc.py > +++ b/utils/raspberrypi/ctt/ctt_alsc.py > @@ -127,11 +127,12 @@ def alsc(Cam, Img, do_alsc_colour, plot=False, grid_size=(16, 12), max_gain=8.0) > channels = [Img.channels[i] for i in Img.order] > """ > calculate size of single rectangle. > - -(-(w-1)//32) is a ceiling division. w-1 is to deal robustly with the case > - where w is a multiple of 32. > + The divisions here must ensure the final row/column of cells has a non-zero number of > + pixels. > """ > w, h = Img.w/2, Img.h/2 > - dx, dy = int(-(-(w-1)//grid_w)), int(-(-(h-1)//grid_h)) > + dx, dy = (w - 1) // (grid_w - 1), (h - 1) // (grid_h - 1) > + > """ > average the green channels into one > """ > -- > 2.34.1 >
Quoting Naushir Patuck (2025-04-28 14:20:26) > Hi David, > > On Mon, 28 Apr 2025 at 11:36, David Plowman > <david.plowman@raspberrypi.com> wrote: > > > > The problem occurs when the calculation could lead to a final row (or > > column) of grid squares with no pixels in them (and hence, NaNs). > > > > One specific case is a Pi 5 with an image width (or height) of 1364, > > so that's 682 Bayer quads. To give 32 grid squares it was calculating > > 22 quads per cell. However, 31 * 22 = 682 leaving nothing in the final > > column. > > > > The fix is to do a rounding-down division by the number of cells minus > > one, rather than a rounding-up division by the number of cells. This > > turns the corner case from one where the final row/column has no > > pixels to one where we don't quite cover the full image, which is how > > we have to handle these cases. > > > > Signed-off-by: David Plowman <david.plowman@raspberrypi.com> > > Reviewed-by: Naushir Patuck <naush@raspberrypi.com> Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Will merge these two. Would you like to add any Bug/Fixes reference so it appears in the libcamera release notes ? -- Kieran > > > --- > > utils/raspberrypi/ctt/ctt_alsc.py | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/utils/raspberrypi/ctt/ctt_alsc.py b/utils/raspberrypi/ctt/ctt_alsc.py > > index 1d94dfa5..f4fd09e3 100644 > > --- a/utils/raspberrypi/ctt/ctt_alsc.py > > +++ b/utils/raspberrypi/ctt/ctt_alsc.py > > @@ -127,11 +127,12 @@ def alsc(Cam, Img, do_alsc_colour, plot=False, grid_size=(16, 12), max_gain=8.0) > > channels = [Img.channels[i] for i in Img.order] > > """ > > calculate size of single rectangle. > > - -(-(w-1)//32) is a ceiling division. w-1 is to deal robustly with the case > > - where w is a multiple of 32. > > + The divisions here must ensure the final row/column of cells has a non-zero number of > > + pixels. > > """ > > w, h = Img.w/2, Img.h/2 > > - dx, dy = int(-(-(w-1)//grid_w)), int(-(-(h-1)//grid_h)) > > + dx, dy = (w - 1) // (grid_w - 1), (h - 1) // (grid_h - 1) > > + > > """ > > average the green channels into one > > """ > > -- > > 2.34.1 > >
diff --git a/utils/raspberrypi/ctt/ctt_alsc.py b/utils/raspberrypi/ctt/ctt_alsc.py index 1d94dfa5..f4fd09e3 100644 --- a/utils/raspberrypi/ctt/ctt_alsc.py +++ b/utils/raspberrypi/ctt/ctt_alsc.py @@ -127,11 +127,12 @@ def alsc(Cam, Img, do_alsc_colour, plot=False, grid_size=(16, 12), max_gain=8.0) channels = [Img.channels[i] for i in Img.order] """ calculate size of single rectangle. - -(-(w-1)//32) is a ceiling division. w-1 is to deal robustly with the case - where w is a multiple of 32. + The divisions here must ensure the final row/column of cells has a non-zero number of + pixels. """ w, h = Img.w/2, Img.h/2 - dx, dy = int(-(-(w-1)//grid_w)), int(-(-(h-1)//grid_h)) + dx, dy = (w - 1) // (grid_w - 1), (h - 1) // (grid_h - 1) + """ average the green channels into one """
The problem occurs when the calculation could lead to a final row (or column) of grid squares with no pixels in them (and hence, NaNs). One specific case is a Pi 5 with an image width (or height) of 1364, so that's 682 Bayer quads. To give 32 grid squares it was calculating 22 quads per cell. However, 31 * 22 = 682 leaving nothing in the final column. The fix is to do a rounding-down division by the number of cells minus one, rather than a rounding-up division by the number of cells. This turns the corner case from one where the final row/column has no pixels to one where we don't quite cover the full image, which is how we have to handle these cases. Signed-off-by: David Plowman <david.plowman@raspberrypi.com> --- utils/raspberrypi/ctt/ctt_alsc.py | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)