# (wrong string) ée

From: <git_AT_suckless.org>
Date: Fri, 20 Jan 2017 16:02:57 +0100 (CET)

Author: Mattias Andrée <maandree_AT_kth.se>
AuthorDate: Fri Jan 20 16:02:49 2017 +0100
Commit: Mattias Andrée <maandree_AT_kth.se>
CommitDate: Fri Jan 20 16:02:49 2017 +0100

Explaination of why blind-set-luma may look weird

Signed-off-by: Mattias Andrée <maandree_AT_kth.se>

diff --git a/src/blind-set-luma.c b/src/blind-set-luma.c
index 71bd59c..49cbc08 100644
--- a/src/blind-set-luma.c
+++ b/src/blind-set-luma.c
_AT_@ -26,7 +26,8 @@ process_xyza(struct stream *colour, struct stream *luma, size_t n)
* so the result may look a bit weird. To change both
* you can use `blind-arithm mul`.
*
- * Explaination:
+ * Explaination of algorithm:
+ *
* Y is the luma, but (X, Z) is not the chroma,
* but in CIELAB, L* is the luma and (a*, *b) is
* the chroma. Multiplying
_AT_@ -50,6 +51,37 @@ process_xyza(struct stream *colour, struct stream *luma, size_t n)
* ⎛1 1 0⎞⎛a 0 0⎞⎛0 1 0⎞ ⎛1 a−1 0⎞
* ⎜1 0 0⎟⎜0 1 0⎟⎜1 −1 0⎟ = ⎜0 a 0⎟.
* ⎝0 0 −1⎠⎝0 0 1⎠⎝0 1 −1⎠ ⎝0 a−1 1⎠
+ *
+ * Explanation of why changing only the luma looks weird:
+ *
+ * Consider when you are workings with colours,
+ * when you want to change the brightness of a
+ * colour, you multiply all parameters: red, green,
+ * and blue, with the same value (this is however
+ * only an approximation in most cases, since you
+ * are usually usally working with colours that
+ * have the sRGB transfer function applied to their
+ * parameters). This action is the same in all
+ * colour models and colour spaces that are a
+ * linear transformation of the sRGB colour spaces
+ * (sans transfer function); this is simply because
+ * of the properties of linear transformations.
+ *
+ * The reason you change brightness this way can
+ * be explained by how objects reflect colour.
+ * Objects can only reject colours that are present
+ * in the light source. A ideal white object will look
+ * pure red if the light sources is ideal red, and a
+ * a ideal blue object will pure black in the same
+ * light source. An object can also not reflect
+ * colours brighter than the source. When the brightness
+ * of a light source is changed, the intensity of all
+ * colours (by wavelength) it emits is multiplied by
+ * one value. Therefore, when changing the brightness
+ * it looks most natural when all primaries (red, green,
+ * and blue) are multiplied by one value, or all
+ * parameters of the used colour spaces is a linear
+ * transformation of sRGB, such as CIE XYZ.
*/
}
}
Received on Fri Jan 20 2017 - 16:02:57 CET

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