[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[gnuastro-commits] master b79fceb 1/2: NoiseChisel warning when the edge
[gnuastro-commits] master b79fceb 1/2: NoiseChisel warning when the edges have a value of zero
Thu, 3 May 2018 14:26:11 -0400 (EDT)
Author: Mohammad Akhlaghi <address@hidden>
Commit: Mohammad Akhlaghi <address@hidden>
NoiseChisel warning when the edges have a value of zero
Most data reduction pipelines put a value of 0.0 where there isn't any data
(commonly on the outer-frames of the observed field). But for NoiseChisel,
a value of 0.0 is meaningful, so it will give bad results. To help early
users understand this important point, a small check was added to see if
the first (and last) two pixels are 0.0 or not. If they are, a complete
warning message will be printed at the start of NoiseChisel's run and even
propose an solution (using Arithmetic).
bin/noisechisel/ui.c | 29 +++++++++++++++++++++++++++--
1 file changed, 27 insertions(+), 2 deletions(-)
diff --git a/bin/noisechisel/ui.c b/bin/noisechisel/ui.c
index 12eebc6..ae74441 100644
@@ -68,8 +68,8 @@ args_doc = "ASTRdata";
doc = GAL_STRINGS_TOP_HELP_INFO PROGRAM_NAME" Detects and segments signal "
"that is deeply burried in noise. It employs a noise-based detection and "
- "segmentation method enabling it to be very resilient to the rich diversity "
- "of shapes in astronomical targets.\n"
+ "segmentation method enabling it to be very resilient to the rich "
+ "diversity of shapes in astronomical targets.\n"
/* After the list of options: */
@@ -521,6 +521,8 @@ ui_prepare_tiles(struct noisechiselparams *p)
ui_preparations(struct noisechiselparams *p)
+ float *f;
/* Prepare the names of the outputs. */
@@ -541,6 +543,29 @@ ui_preparations(struct noisechiselparams *p)
"can only operate on 2D datasets (images)", p->inputname, p->cp.hdu,
+ /* A small check to see if the edges of the dataset aren't zero valued:
+ they should be masked. */
+ if( (f==0.0 && f==0.0)
+ || (f[ p->input->size-1 ]==0.0 && f[ p->input->size-2 ]==0.0) )
+ error(0, 0, "%s (hdu %s): [*** WARNING ***]: The first and/or last few "
+ "pixels have a value of 0.0. As described below, the result of "
+ "this run may thus not be reasonable/optimal.\n\n"
+ "Some data reduction pipelines put 0.0 where there isn't data "
+ "(most commonly on the edges). However, NoiseChisel's "
+ "noise-based detection paradigm starts from the lower values of "
+ "the dataset (not high S/N peaks): its initial threshold is "
+ "mostly below the Sky value (0.0 in processed images). Therefore "
+ "0.0 is meaningful for NoiseChisel and must not be used for a "
+ "blank value.\n\n"
+ "To ignore certain pixels, they must have a blank/NaN value. "
+ "To mask (set to blank/NaN) the 0.0 valued elements, you can use "
+ "Gnuastro's Arithmetic program with a command like this:\n\n"
+ " $ astarithmetic %s %s 0.0 eq nan where -g%s\n\n"
+ "If the few 0.0 valued pixels on the edges are meaningful for "
+ "your analysis, please ignore this warming message.\n"
+ p->inputname, p->cp.hdu, p->inputname, p->inputname, p->cp.hdu);
/* If a convolved image was given, read it in. Otherwise, read the given