[README.md] updates for v4.0.0 release

README.md

@@ -8,17 +8,17 @@
 
 Crunch is a tool for lossy PNG image file optimization.  It combines selective bit depth, color type, and color palette reduction with zopfli DEFLATE compression algorithm encoding using the pngquant and zopflipng PNG optimization tools.  This approach leads to a significant file size gain relative to lossless approaches at the expense of a relatively modest decrease in image quality (see [example images](#examples) below).
 
-Historical benchmarks with the files included in Cédric Louvrier's [PNG Test Corpus](https://css-ig.net/png-tools-overview) versus other commonly used PNG optimization software are available in [BENCHMARKS.md](docs/BENCHMARKS.md).
+Continuous benchmark testing is available on [Travis CI](https://travis-ci.com/chrissimpkins/Crunch) (open the Benchmarks build for the commit of interest). Please see the benchmarks directory of this repository for details about the benchmarking approach and instructions on how to execute benchmarks locally on the reference images distributed in this repository or with your own image files.
 
-Crunch PNG image optimization is available through the following applications in this repository:
+Crunch PNG image optimization is available through the following applications that are distributed in this repository:
 
-- [`crunch`](docs/EXECUTABLE.md) - a *nix command line executable that can be used on macOS, Linux, and Windows POSIX application deployment environments such as Cygwin
+- [`crunch`](docs/EXECUTABLE.md) - a *nix command line executable that can be used on macOS, Linux, and Windows POSIX application deployment environments such as Cygwin or the Windows subsystem for Linux
 - [Crunch GUI](docs/MACOSGUI.md) - a native macOS drag and drop GUI tool
 - [Crunch Image(s)](docs/SERVICE.md) service - a macOS right-click menu service for PNG images selected in the Finder
 
-## Install and Usage
+## Installation and Usage
 
-Install and usage documentation links for each of the Crunch applications are available below.
+Installation and usage documentation links for each of the Crunch applications are available below.
 
 ## `crunch` Command Line Executable
 
@@ -50,15 +50,15 @@ Select one or more PNG images in the Finder, right-click, and select the `Servic
 
 ## Examples
 
-The following examples demonstrate the benefits and disadvantages of the current iteration of Crunch's aggressive space saving optimization strategy.  In many cases, the PNG optimization minimizes file size with an imperceptible decrease in image quality.  In some cases, degradation of image quality is visible. View the horizon line in the prairie photo below for a demonstration of an undesirable artifact that is introduced with image processing.  Experiment with the image types that you use and please submit a report with examples of any images where the image quality falls short of expectations for production-ready files.
+The following examples demonstrate the benefits and disadvantages of the current iteration of Crunch's aggressive space saving optimization strategy.  The optimized image files are updated at every Crunch release.  In many cases, the PNG optimization decreases file size with an imperceptible impact on image quality.  In some cases, degradation of image quality is visible. Visual confirmation of image quality is highly recommended with lossy optimization tools in production settings.
 
 ## Photography Examples
 
 ### Cat Image
 
 - Original Size: 583,398 bytes
 - Optimized Size: 196,085 bytes
-- DSSIM similarity score: 0.001471
+- DSSIM similarity score: 0.001383
 - Percent original size: 33.61%
 
 ##### Original
@@ -73,7 +73,7 @@ The following examples demonstrate the benefits and disadvantages of the current
 
 - Original Size: 138,272
 - Optimized Size: 66,593
-- DSSIM similarity score: 0.000948
+- DSSIM similarity score: 0.000920
 - Percent original size: 48.16%
 
 ##### Original
@@ -89,7 +89,7 @@ The following examples demonstrate the benefits and disadvantages of the current
 
 - Original Size: 196,794 bytes
 - Optimized Size: 77,965 bytes
-- DSSIM similarity score: 0.002988
+- DSSIM similarity score: 0.002923
 - Percent original size: 39.62%
 
 ##### Original
@@ -108,7 +108,7 @@ The following examples demonstrate the benefits and disadvantages of the current
 
 - Original Size: 197,193 bytes
 - Optimized Size: 67,596 bytes
-- DSSIM similarity score: 0.000162
+- DSSIM similarity score: 0.003047
 - Percent original size: 34.28%
 
 ##### Original
@@ -123,7 +123,7 @@ The following examples demonstrate the benefits and disadvantages of the current
 
 - Original Size: 249,251 bytes
 - Optimized Size: 67,135 bytes
-- DSSIM similarity score: 0.002491
+- DSSIM similarity score: 0.002450
 - Percent original size: 26.93%
 
 ##### Original
@@ -139,7 +139,7 @@ The following examples demonstrate the benefits and disadvantages of the current
 
 - Original Size: 440,126 bytes
 - Optimized Size: 196,962 bytes
-- DSSIM similarity score: 0.000480
+- DSSIM similarity score: 0.001013
 - Percent original size: 44.75%
 
 ##### Original
@@ -152,6 +152,8 @@ The following examples demonstrate the benefits and disadvantages of the current
 
 All images above were obtained from [Pixabay](https://pixabay.com) and are dedicated to the public domain under the [CC0 Public Domain Dedication](https://creativecommons.org/publicdomain/zero/1.0/).
 
+DSSIM testing was performed with v2.10.0 of the [kornelski/dssim tool](https://github.com/kornelski/dssim).
+
 ## Issue Reporting
 
 Have you identified a problem? Please [create a new issue report](https://github.com/chrissimpkins/Crunch/issues/new/choose) on the Github issue tracker so that we can address it.