Commit a5375eee authored by scott's avatar scott
Browse files

Made use of quotes consistent. Added a section on layer masks. Some

other miscellanous tweaking.

--sg
parent 12e7bc16
......@@ -118,7 +118,7 @@ image must be compatible with the image type.
A \emph{drawable} is a linear array of pixel data; however, the
contents of a drawable need not necessarily be used solely for
rendering as pixel data (for example, selection masks are drawables
internal to the program, and they are not directly `paintable' by the
internal to the program, and they are not directly ``paintable'' by the
user).
Each drawable contains from one to four data channels (not to be
......@@ -154,8 +154,20 @@ as the image type with an added alpha channel (for example, a
grayscale image cannot contain an RGB layer). Every layer is part of
exactly one image.
The user may selectively make any layer of an invisible; invisible
layers do not contribute to the composition process.
\subsubsection{Layer masks}
Optionally, any layer with an alpha channel may have an added
\emph{layer mask}. The layer mask is a separate channel which is
multiplied into that layer's drawable alpha channel whenever that
layer contributes to a projection. The user can elect to temporarily
disable this effect of a layer mask for editing purposes, or cause the
layer mask to be substituted for the main drawable; these effects are
mainly for convenience in editing. The user can also merge the layer
mask back into the layer's main drawable, or discard it.
\subsection{Channels}
The term ``channels'' actually refers to three different things in the
......@@ -165,18 +177,19 @@ interpretation of these values varies depending on the type of
channel.
In addition to these channel types, each image also has either one or
three `virtual' channels (one for grayscale and indexed images, three
for RGB). The virtual channels are merely a convenience to the user;
they are not drawables by themselves. As with the custom channels,
the virtual ones can be made active or inactive (visible or
invisible). Normally all the virtual channels are active, all
painting operations modify each of the channels. When a channel is
inactive, painting operations will ignore that channel.
This is useful in two situations. First, when the user wants to see
only a subset of the color channels (RGB). Second, when the user
wants to paint on the image but only modify a subset of the channels
instead of all of them.
three ``virtual'' channels (one for grayscale and indexed images,
three for RGB). These virtual channels (sometimes called ``color
channels'') are merely a convenience to the user and are not drawables
by themselves. These virtual channels can be made visible or
invisible, and for images where there is more than one virtual
channel, each can be made visible or invisible independently of the
others. Normally all the virtual channels are active, and all
painting operations modify all three the channels. When a virtual
channel is invisible, both layer composition and layer painting
operations ignore that channel. This is useful in two situations:
first, when the user wants to see only a subset of the color channels
(RGB); and second, when the user wants to paint on the image but only
modify a subset of the channels.
\section{Tiles}
......@@ -240,7 +253,7 @@ replicate) that make creation of custom gradients easy and convenient.
The color segments support full transparency information, making for
even more flexible gradients.
To avoid sampling artifacts (the `jaggies'), the gradient rendering
To avoid sampling artifacts (the ``jaggies''), the gradient rendering
engine supports adaptive supersampling with customizable threshold and
recursion depth parameters. With adaptive supersampling even the most
complex custom gradients will be rendered smoothly without
......
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