Add README

README.md

@@ -0,0 +1,56 @@
+# Goptimizer - downscales and optimizes images
+
+Goptimizer is a commandline utility written in Golang. It downscales and optimize existing images JPEG, PNG and Gif files.
+
+Image downscaling is done within Goptimize (`-m <width>x<height>`, see [Usage](#usage-options)), however optimization is done using the following additional tools (if they are installed):
+
+- jpegoptim
+- jpegtran (`libjpeg-turbo-progs`)
+- optipng
+- pngquant
+- gifsicle
+
+
+## Notes
+
+Both `jpegoptim` & `jpegtran` have almost identical optimization, so if both are installed then just `jpegtran` is used for JPG optimization. PNG optimization however will run through both `optipng` & `pngquant` (if installed) as this has definite advantages.
+
+It is highly recommended to install the necessary optimization tools, however they are not required to run goptimize.
+
+Goptimize will remove all exif data from JPEG files, auto-rotating those that relied on it.
+
+It will also preserve (by default) the file's original modification times (`-p=false` to disable).
+
+
+## Usage options
+
+```
+Usage: ./goptimize [options] <images>
+
+Options:
+  -gifsicle string
+        gifsicle binary (default "gifsicle")
+  -jpegoptim string
+        jpegoptim binary (default "jpegoptim")
+  -jpegtran string
+        jpegtran binary (default "jpegtran")
+  -m string
+        downscale to a maximum width & height in pixels (<width>x<height>)
+  -o string
+        output directory (default overwrites original)
+  -optipng string
+        optipng binary (default "optipng")
+  -p    preserve file modification times (default true)
+  -pngquant string
+        pngquant binary (default "pngquant")
+  -q int
+        quality - JPEG only (default 75)
+```
+
+
+## Examples
+
+- `./goptimize image.png` - optimize a PNG file
+- `./goptimize -m 800x800 *` - optimize and downscale all image files to a maximum size of 800x800px
+- `./goptimize -m 1200x0 image.jpg` - optimize and downscale a JPG file to a maximum size of width of 1200px
+- `./goptimize -o out/ image.jpg` - optimize a JPG file and save it to `out/`