<h3>Contents</h3>
</div>
<ul>
- <li><a href='#Babl'>Babl</a></li>
+ <li><a href='#Download'> Download</a></li>
<li><a href='#Features'> Features</a></li>
+ <li><a href='#ColorManagement'> Color Management</a></li>
<li><a href='#Symmetric-Alpha'> Symmetric-Alpha</a></li>
<li><a href='#CMYK'> CMYK</a></li>
- <li><a href='#ColorManagement'> Color Management</a></li>
- <li><a href='#Download'>Download</a></li>
<!--<li><a href='#Background'>Background</a></li>-->
- <li><a href='#Documentation'>Documentation</a></li>
<li><a href='#Usage'> Usage</a></li>
<li><a href='#Vocabulary'> Vocabulary</a></li>
<!--<li><a href='#Data-types'> Data types</a></li>
<li><a href='#Extending'> Extending</a></li>
<li><a href='#DirectoryOverview'> Directory Overview</a></li>
<!--<li><a href='#ColorManagement'>Color Management</a></li>-->
- <li><a href='#TODO'>Todo</a></li>
- <li><a href='#Copyright'>Copyright</a></li>
+ <li><a href='#TODO'> Todo</a></li>
+
+ <li><a href='#Copyright'> Copyright</a></li>
<li><a href='#Authors'> Authors</a></li>
</ul>
</div>
<li>ANSI C without external dependencies, works on win32, linux and mac,
32bit and 64bit systems.</li>
<li>Stable, small API, with singleton objects returned.</li>
- <li>Extendable with new formats, color models, components
- and datatypes.</li>
+ <li>Extendable with new formats, color models, components and datatypes.</li>
<li>Can load <a href='#ColorManagement'> Color
-Spaces</a></li> rom ICC v2 and v4 profiles containing RGB matrix + TRC, or <a
+Spaces</a></li>
from ICC v2 and v4 profiles containing RGB matrix + TRC, or <a
href='#CMYK'>CMYK</a> profiles.</li>
<li><a href='#Symmetric-Alpha'>Symmetric-Alpha</a> no loss of color fidelity due to asymptotic behavior near alpha 0.0 in floating point.</li>
<li>Reference 64bit floating point conversions for datatypes and color
models, with 32bit floating point reference speed-ups in some places.
</li>
- <li>Self profiling/validating and optimizing, optimizing accuracy and
-performance at runtime when the best performing single or multi-step conversion
-path is chosen. This permits additional SIMD optimiations paths to be added and
-to ones supported are competing with each other.</li>
+ <li>Runtime profiling/validating and code-path optimizing with persistence of profiling data across runs, with caching of results.</li>
</ul>
<p><a href='http://www.gegl.org/'>GEGL</a> through <a
<!--NEWS-->
For more news see git log.
- <a name='Documentation'></a>
- <h2>Documentation</h2>
+
+ <a name='ColorManagement'></a>
+ <h2>Color Management</h2>
+
+ <p>All pixel formats in babl have a specified color space, if NULL is passed
+as a space constants for (unbounded) linear sRGB data is assumed, data being
+sRGB defines the conversion to and from gray-scale as well as the gamma
+ - or Transfer Response Curve, TRC, used for converting between linear and
+ non-linear variants of the data.</p>
+
+ <p>babl has API for creating a format for a specific space:
+<tt>babl_format_with_space("R'G'B' u16", babl_space ("Rec2020"))</tt> creates a
+16 bit integer format for the Rec2020 color space. Babl knows internally about
+"sRGB", "Rec2020", "Adobe", "Apple", "ProPhoto", "ACEScg" and "ACES2065-1"
+spaces, as they are defined with constants on their wikipedia pages or similar upstream references.</p>
+
+ <p>Additional spaces can be loaded from monitor-class matrix+TRC ICC v2 and
+ v4 profiles. Using babl_icc_make_space (see babl.h for details). The space of
+ a babl format can also be queried with babl_format_get_space.
+ </p>
+
+ <a name='Symmetric-Alpha'></a>
+ <h2>Symmetric transformations for floating point alpha</h2>
+
+
+ <p> babl clamps the alpha used when going from separate alpha to associated
+alpha or from associated alpha to separate alpha to BABL_ALPHA_FLOOR. This
+replaces asymptotic behavior and direct precision loss of color precision when
+multiplying or dividing by alphas near 0.0 with a consistent symmetric
+transformation.</p>
+
+<p>Original intent of data as well as non-asymptotic precision loss is thus
+maintained when the processing chain might temporarily use the other alpha
+representation.</p>
+
+<pre>
+ #define BABL_ALPHA_FLOOR (1.0/65536.0)
+ #define BABL_ALPHA_FLOOR_F (1.0f/65536.0f)
+</pre>
+
+<p>The deviation from not clamping near 0.0 is within the quantization margin
+of 16bit integer alpha, thus no adaptations for any SIMD or and similar 8bit
+and 16bit extensions of pixel format conversions are needed.
+ </p>
+
+ <p>This is the clamping function in use:</p>
+<pre>
+static inline float
+babl_epsilon_for_zero_float (float value)
+{
+ if (value <= BABL_ALPHA_FLOOR_F)
+ {
+ /* for performance one could directly retun BABL_ALPHA_FLOOR_F here
+ and dropping handling negative values consistently. */
+ if (value >= 0.0f)
+ return BABL_ALPHA_FLOOR_F;
+ else if (value >= -BABL_ALPHA_FLOOR_F)
+ return -BABL_ALPHA_FLOOR_F;
+ }
+ return value; /* most common case, return input value */
+}
+</pre>
+<p>And an example use of this clamping function that is consistent with babls behavior:</p>
+<pre>
+static inline void
+associated_to_separate_rgba (const float *associated_rgba,
+ float *separate_rgba)
+{
+ float alpha = associated_rgba[3];
+ float clamped_alpha = babl_epsilon_for_zero_float (alpha);
+ float reciprocal_alpha = 1.0f / clamped_alpha;
+
+ separate_rgba[0] = associated_rgba[0] * reciprocal_alpha;
+ separate_rgba[1] = associated_rgba[1] * reciprocal_alpha;
+ separate_rgba[2] = associated_rgba[2] * reciprocal_alpha;
+ separate_rgba[3] = alpha;
+}
+</pre>
+
+
+<p>For more detils see <a href='https://gitlab.gnome.org/GNOME/babl/commit/a4d607843d3cab18745d547fc8a46dec51dcea5e'>the commit message of the most recent refinement</a> as well as <a href='https://www.patreon.com/posts/premultiplied-in-21014115'>blog post with further background</a>.</p>
+
+
+ <a name='CMYK'></a>
+ <h2>CMYK</h2>
+
+ <p>CMYK handling is done using babl-spaces created with ICC profiles
+containing CMYK profiles. BablSpaces for these ICC profiles handle color conversions using lcms2 - or if compiled without lcms2 support a naive profile independent fallback.</p>
+ <p>When a babl space derived from a CMYK ICC profile is used to instantiate
+RGB formats, the resulting formats are using the default/NULL space for
+primaries and TRCs.</p>
+
+ <p>The CMYK formats that use lcms2 for color interchange with the rest of
+babl are the following, which are available for all data types, u8, u16, half
+and float:</p>
+ <dl>
+ <dt>CMYK</dt><dd>Cyan Magenta Yellow Key, with 0 being white and 1.0 full ink coverage.</dd>
+ <dt>CMYKA</dt><dd>as previous, with separate alpha channel</dd>
+ <dt>CaMaYaKaA</dt><dd>as previous but associated alpha</dd>
+ <dt>cmyk</dt><dd>inverted CMYK, where 0.0 is full ink coverage and 1.0 is none</dd>
+ <dt>cmykA</dt><dd>as previous, with separate alpha channel</dd>
+ <dt>camayakaA</dt><dd>as previous but associated alpha</dd>
+ </dl>
+
+ <a name='Usage'></a>
+ <h2>Usage</h2>
<p>When using BablFishes to do your conversions, you request a fish to
convert between two formats, and an optimal fish to babls capability is
provided that you can use to do your conversions. Babl also provides
not take much time and will speed up babl for other users as well.
</p>
- <a name='Usage'></a>
- <h3>Usage</h3>
-
<pre
><span class='function'>babl_process</span> <span class='paren'>(</span><span class='function'>babl_fish</span> <span class='paren'>(</span>source_format, destination_format<span class='paren'>)</span>,
source_buffer, destination_buffer,
</pre>
-->
- <a name='ColorManagement'></a>
- <h2>Color Management</h2>
-
- <p>All pixel formats in babl have a specified color space, if NULL is passed
-as a space constants for (unbounded) linear sRGB data is assumed, data being
-sRGB defines the conversion to and from gray-scale as well as the gamma
- - or Transfer Response Curve, TRC, used for converting between linear and
- non-linear variants of the data.</p>
-
- <p>babl has API for creating a format for a specific space:
-<tt>babl_format_with_space("R'G'B' u16", babl_space ("Rec2020"))</tt> creates a
-16 bit integer format for the Rec2020 color space. Babl knows internally about
-"sRGB", "Rec2020", "Adobe", "Apple", "ProPhoto", "ACEScg" and "ACES2065-1"
-spaces, as they are defined with constants on their wikipedia pages or similar upstream references.</p>
-
- <p>Additional spaces can be loaded from monitor-class matrix+TRC ICC v2 and
- v4 profiles. Using babl_icc_make_space (see babl.h for details). The space of
- a babl format can also be queried with babl_format_get_space.
- </p>
-
- <a name='Symmetric-Alpha'></a>
- <h2>Symmetric transformations for floating point alpha</h2>
-
-
- <p>
- babl clamps the alpha used when going from separate alpha to associated alpha
-or from associated alpha to separate alpha to BABL_ALPHA_FLOOR. This avoids
-asymptotic behavior and direct precision loss of color precision when multiplying or dividing by alphas near 0.0.</p>
-
-<p>Original intent of data as well as non-asymptotic precision loss is thus
-maintained when the processing chain might temporarily use the other alpha
-representation.</p>
-
-<pre>
- #define BABL_ALPHA_FLOOR (1.0/65536.0)
- #define BABL_ALPHA_FLOOR_F (1.0f/65536.0f)
-</pre>
-
-<p>The deviation from not clamping near 0.0 is within the quantization margin
-of 16bit integer alpha, thus no adaptations of are introduced for the 8bit and 16bit versions of pixel format conversions were needed.
- </p>
-
- <p>This is the clamping function:</p>
-<pre>
-
- static inline float
- babl_epsilon_for_zero_float (float value)
- {
- if (value <= BABL_ALPHA_FLOOR_F)
- {
- /* for performance one could directly retun BABL_ALPHA_FLOOR_F here
- and dropping handling negative values consistently. */
- if (value >= 0.0f)
- return BABL_ALPHA_FLOOR_F;
- else if (value >= -BABL_ALPHA_FLOOR_F)
- return -BABL_ALPHA_FLOOR_F;
- }
- return value; /* most common case, return input value */
- }
-</pre>
-<p>And an example use of this clamping function that is consistent with babls behavior:</p>
-<pre>
- static inline void
- associated_to_separate_rgba (const float *associated_rgba,
- float *separate_rgba)
- {
- float alpha = associated_rgba[3];
- float clamped_alpha = babl_epsilon_for_zero_float (alpha);
- float reciprocal_alpha = 1.0f / clamped_alpha;
-
- separate_rgba[0] = associated_rgba[0] * reciprocal_alpha;
- separate_rgba[1] = associated_rgba[1] * reciprocal_alpha;
- separate_rgba[2] = associated_rgba[2] * reciprocal_alpha;
- separate_rgba[3] = alpha;
- }
-</pre>
-
-
-<p>For more detils see <a href='https://gitlab.gnome.org/GNOME/babl/commit/a4d607843d3cab18745d547fc8a46dec51dcea5e'>the commit message of the most recent refinement</a> as well as <a href='https://www.patreon.com/posts/premultiplied-in-21014115'>blog post with further background</a>.</p>
-
-
- <a name='CMYK'></a>
- <h2>CMYK</h2>
-
- <p>CMYK handling is done using babl-spaces created with ICC profiles
-containing CMYK profiles. BablSpaces for these ICC profiles handle color conversions using lcms2 - or if compiled without lcms2 support a naive profile independent fallback.</p>
- <p>When a babl space derived from a CMYK ICC profile is used to instantiate
-RGB formats, the resulting formats are using the default/NULL space for
-primaries and TRCs.</p>
-
- <p>The CMYK formats that use lcms2 for color interchange with the rest of
-babl are the following, which are available for all data types, u8, u16, half
-and float:</p>
- <dl>
- <dt>CMYK</dt><dd>Cyan Magenta Yellow Key, with 0 being white and 1.0 full ink coverage.</dd>
- <dt>CMYKA</dt><dd>as previous, with non-associated alpha channel</dd>
- <dt>CaMaYaKaA</dt><dd>as previous but premultiplied/associated alpha</dd>
- <dt>cmyk</dt><dd>inverted CMYK, where 0.0 is full ink coverage and 1.0 is none</dd>
- <dt>cmykA</dt><dd>as previous, with non-associated alpha channel</dd>
- <dt>camayakaA</dt><dd>as previous but premultiplied/associated alpha</dd>
- </dl>
<a name='Vocabulary'></a>
projects / babl.git / commitdiff