Remove unnecessary content from the techref for patterns

Author: seisman

doc/techref/patterns.md

@@ -1,24 +1,7 @@
-# Bit and Hachure Patterns
+# 90 Predefined Bit and Hachure Patterns
 
 PyGMT supports a variety of bit and hachure patterns that can be used to fill polygons.
-
-These patterns can be defined using the following syntax:
-
-**P**|**p**_pattern_[**+b**_color_][**+f**_color_][**+r**_dpi_]
-
-*pattern* can either be a number in the range 1-90 or the name of a 1-, 8-, or 24-bit
-image raster file. The former will result in one of the 90 predefined 64x64 bit-patterns
-provided by GMT (see the figure below). The latter allows the user to create customized,
-repeating images using image raster files.
-
-By specifying uppercase **P** instead of **p** the image will be bit-reversed, i.e.,
-white and black areas will be interchanged (only applies to 1-bit images or predefined
-bit-image patterns). For these patterns and other 1-bit images one may specify
-alternative **b**ackground and **f**oreground colors (by appending **+b**_color_ and/or
-**+f**_color_) that will replace the default white and black pixels, respectively.
-Excluding *color* from a fore- or background specification yields a transparent image
-where only the back- or foreground pixels will be painted. The **+r**_dpi_ modifier sets
-the resolution in dpi.
+These patterns can be specified via the {class}`pygmt.params.Pattern` class.
 
 The image below shows the 90 predefined bit patterns that can be used in PyGMT.