RIOT - Radical Image Optimization Tool

by Lucian Sabo

Official website: http://luci.criosweb.ro/riot/

Saving images for web/email/other media with the best compression ratio and quality is a difficult task if you don’t have the right tools. Choosing the right format then choosing the right parameters are the key factors of smaller files. Previewing the resulting image and the projected filesize will help the user choose the best settings. This kind of image optimization software is often called “Save for web”.

IrfanView users: Acces RIOT plugin from IrfanView by selecting File->Save for web.

RIOT key features:

open multiple graphic file formats by looking first at the magic number (it does not need file extension to recognize format)including support for uncommon images types (up to 128 BPP, integer and floating point. EX: hdr images, 16 bit grayscale, etc). Adaptive logarithmic tone mapping algorithm (Drago) used for HDR images
save and optimize JPEG, GIF and PNG with a simple, clean user interface
works in dual view: (original - optimized image) or single view (optimized image). Automatic preview of resulting image
compress files to desired filesize threshold
fast processing (all is done in memory); see instant results including resulting filesize
decide if you want to keep metadata (comments, IPTC, Adobe XMP, EXIF profiles, ICC profiles). Unsupported metadata is removed
common tools: pan and zoom, rotate, flip
resize image by using well known resample filters (ex: Lanczos3, Catmull Rom, Bicubic, and others)
in-place compare function (alternativelly display the original image over the optimized image to notice small pixel changes)
the compression and the results are comparable to those of commercial products.

Input image types

common bitmap images as well as Adobe Photoshop PSD files.

Optimization details

JPEG settings

In RIOT you can find the following JPEG settings:

quality (compression)
advanced chroma subsampling (none,low 4:2:2,medium 4:2:0,high 4:1:1)
save as 8bit grayscale
save progressive

Supported output bit depths: 24 bit color, 8 bit grayscale

GIF settings

The following GIF settings are currently implemented:

color reduction
- color quantization downto 256..2 colors (no color dithering support) current color quantization algorithms are: Xiaolin Wu and NeuQuant neural net
- grayscale 8bit palette
- floyd-steinberg dithered 1bit monochrome
save interlaced

Supported output bit depths: 8 bit color, 8 bit grayscale

PNG settings

The following PNG settings are currently implemented:

true color support (24 bit RGB, 32 bit RGBA)
color reduction
- color quantization downto 256..2 colors (no color dithering support) current color quantization algorithms are: Xiaolin Wu and NeuQuant neural net
- grayscale 8bit palette
- floyd-steinberg dithered 1bit monochrome
save interlaced
maximum ZLIB compression flag

Automatic pnglib filtering optimizations apply.

Supported output bit depths: 8, 24, 32 bit color, 8 bit grayscale

Metadata settings

Choose to keep or remove the following metadata:

comments
Adobe XMP info
IPTC info
EXIF profile (including GPS and maker notes)
ICC color profiles

Unknown or unsupported metadata is automatically removed.

Mask settings

The program lets you choose several transparency options:

Keep transparency
(use threshold for conversion from alpha to indexed transparency)
Blend with solid background
(choose a color for blending the transparency into the background (alpha composition))
Set opaque
(remove transparency information by making all pixels opaque)

Known issues:

4bpp output is not supported

Future plans:

Adobe Photoshop Filter support (8BF) - add GML Matting plugin for object extraction.
twain scanner support
basic image processing (brightness, contrast, etc)
jpeg smoothening
PNG compression optimizations (I need time for this)
define transparent regions (with variable transparency)
crop function
overlay image watermark

Please arange these priotities according to your needs and let me know.

Available as stand-alone executable (portable app) or dynamic link library for developers. The plugin is already included into the best image viewer worldwide (in my oppinion) - IrfanView. This software uses a modified version of FreeImage open source image library. See http://freeimage.sourceforge.net for details. FreeImage is used under the FIPL license version 1.0.