Edge Overlay Notes - Canon CHDK User Manual

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With this setting no Bad pixel removal processing takes place.
[Off]
With this setting CHDK calculates the color for the bad pixel based on its four neighbor
[Average]
pixels with a simple average calculation and then interpolates - bad neighbor pixels will be ignored in this
calculation.
This setting means - intended for use with post processing raw converter software to remove
[RawConv]
the bad pixels later in the workflow. With this setting CHDK just sets the bad pixel to the value 0 (zero),
without any other calculation or modification. Most RAW-capable apps. will detect this and apply their
own algorithms. This option is ignored in DNG mode (in DNG mode bad pixels are always averaged by
CHDK).
Quote from senior developer ewavr - 'You can compare bad pixel removal quality in both modes, IMO,
"RAWConv" mode is preferred, because CHDK interpolation is very unsophisticated'.
Note: With DNG format enabled, bad pixels identified by badpixel.bin are always removed -
(interpolated / averaged) by CHDK. This does not affect the "Bad pixel removal" option, which also
fixes user specified pixels.
Forum discussion:
http://chdk.setepontos.com/index.php?topic=3098.msg28955#msg28955
re: "Average" and RAWconv"
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Edge overlay notes

Description for builds prior to 0.9.9 r928 - (original code and part of description from early CHDK
developer hiker_jon)
A valuable feature for anyone needing to align features for panorama stitching or for doing stop-frame
animations. Similar to an "onion-skinning" mode (see Google) in animation software. During shoot mode
half or full press this feature adds an overlay based on the image edges, additionally a grid that matches
the Canon frame is added.
<ALT>
Use the left, right, up or down buttons to shift the overlay (use it in mode to avoid changing the
Canon options). The edge overlay is frozen when taking a shot. The frozen edges are displayed from
then on when the shutter gets half-pressed, FROZEN is shown in the OSD. When you shoot again it goes
back to the original behavior - showing the edges of the current image on half-press. This behavior is
useful when shooting stereo pairs. For panoramas you would want to freeze the edges after every full
press. Zebra mode should be disabled when using the Edge overlay.
During the later part of 2010, developer ultimA gave the Edge overlay a major overhaul, (with input
from forum member f_m_b), adopted in changeset 0.9.9 r928, Some of the changes are visible to the
user, such as some new menu entries and a new order of the entries. Other important changes are less
visible, such as rewriting of the code and its effect on the use of the Edge overlay, mainly the changes to
memory use, and the "Sobel" edge detecting method. Cameras with low memory reserves can now use
Edge overlay without the crashes experienced before the changes.