blemishes

(Compiled by DL)

Purpose: Generates BLEMISH files which mask bad pixels in individual or multiple images.

This procedure creates a blemish (.BLM) file for an image that lives in the BLEMISHES subdirectory.

Requires

• BLEMISHES/ - Directory containing BLEMISH files for individual images and BLEMISH templates for multiple affected images.

• SUMFILES/ - Directory containing the SUMFILE for the image to mask, blemishes reads NPX (number of pixels), and NLN (number of lines);

• INIT_LITHOS - blemishes reads the parameter BLEMISH (if it exists), which references any existing template for masking bad pixels common to multiple images.

  • BLEMISHES/TEMPLATENAME.BLM - template BLEMISH file for each INIT_LITHOS BLEMISH entry.

Optional

• BLEMISH/PICNM.BLM - Existing image BLEMISH file for deletion or editing.

Output

• TEMPFILE.pgm -

• BLEMISHES/PICNAME.BLM - Generated or edited BLEMISH (.BLM) file;

Using blemishes

(The following section is taken from SPOC v3.02A PDF/LITHOSPHERE/blemishes.f File Reference, rearranged for convenience.)

 Input 12-character picture name
P3T11S2H0409
 gc TEMPFILE.pgm

 b. Block
 s. Spot
 q. Quit

There are two kinds of blemish handled here:

The block option (b) masks a square block of the image specified by a minimum and maximum pixel and line. This type of blemish is typically used for missing or hashy lines due to downlink errors.

The spot option (s) masks a small region around a pixel/line center (p,l) from p-k to p+k and l-k to l+k. An additional input is a brightness threshold. If this is chocen as zero, everything in the spot will be masked. However, if there is a bright blemish such as a cosmic ray hit in the spot, the threshold can be set to remove only the affected pixls. In the latter case, a large region (large k) can be specified and all the bright blemishes in the region masked without affecting the rest of the data.

Block Blemish

 Input pxmn, pxmx, lnmn, lnmx

• pxmn, pxmx: must be in the range [1:NPX] (where NPX is the number of pixels in image).

• lnmn, lnmx: must be in the range [1:NLN] (where NLN is the number of lines in image).

 Input 12-character picture name
P3T11S2H0409
 Remove existing blemish file? (y/n)

BLEMISH Templates

In the event that a camera has bad pixels common to all images, a template can be created that masks these pixels in all that camera's images. The template is specified in the INIT_LITHOS.TXT file with the key word BLEMISH. For example, DAWN has two framing cameras with image names starting with FC1 and FC2. FC2 images all have several blemishes in the same places. A template in INIT_LITHOS specified by BLEMISH='FC2#########' will correct all of these mages without having thousands of individual blemish files. If an image contains additional blemishes it can have its own file with just those additional blemishes.

In order to create a TEMPLATE, a blemish file for one of the affected images is made with only the common bad areas masked. That file can be saved or not (the procedure will ask: 'Save blemish file? (y/n)'), and then the user will be asked 'Create/change template file? (y/n)'. If 'y' is chosen the user will be asked for a 12 character template name with the common characters of the image names in their proper positions and # everywhere else. If the PICNM used to make the original blemish file is not consistent with the template, the procedure will say so and STOP. Otherwise, it will create the template file and, if necessary, remind the user to define it in INIT_LITHOS.TXT.