Best Free Windows 64-bit Image Tools

Best Free Windows 64-bit Image Editor

"Paint.NET makes a very good mid-level photo retouching choice.  It has a nice set of photo correction tools including curves, and levels.  It has a very nice implementation of layers complete with blending modes, and adjustable opacity/transparency levels.  It has a fairly full pallet of selection, painting, and shape drawing tools. It is completed with a selection of filters for adding special effects to your images.  All in all, it offers a lot for a free image retouching software. … In addition to the products built in features there are a huge number of user contributed plugins that add further capabilities. … Paint.NET isn't too resource intensive and during testing I didn't notice slow downs at any point." 
"GIMP is currently the only freeware package I am aware of that can be called an advanced image editor.  It has a steeper learning curve than the previously reviewed editors, but it is feature rich.  It's multi-windowed interface makes it a little unusual for a windows program. If you are inexperienced at using image editing programs GIMP will likely be too overwhelming to start learning on, so I would suggest beginning with one of the basic, or mid-level editors." 
The 64-bit version I have used is labelled unstable but I have had no problems so far. There is at least one other 64-bit version which I will review at a later date. Both versions are likely to be faster than 32-bit GIMP particularly when working with large images.
Lightbox Image Editor is a basic editor that "has an attractive user interface that is simple and straight forward, and offers intuitive slide-bar adjustments for your images.  It also has split screen views to help you compare your images before and after the corrections have been made.  It includes simple tools to correct red-eye, sharpen, crop, re-size, add borders, and print."  

Best Free Windows 64-bit Image Viewer

Zoner Photo Studio "appears very professional and can even seem a bit daunting with all those menus, tabs and icons, but it's very intuitive and tooltips show up for everything. Comprehensive help and links to video tutorials are provided as well. It's organized into a manager (a thumbnail view with a folder tree and general information), a fullscreen viewer and an editor, which is quite stripped down compared to the paid version but still very functional. … the editor has a variety of tools like a handy clone stamp, a funny morph mesh and great effects that can be applied on selected areas. You can also organize into albums, geotag, build calendars, stitch panoramas, make 3D pictures and a lot of other things. Moreover, it reads many formats, including RAW, and writes to the ten most commonly used." 
XnView is "probably the most versatile of all viewers because it can read nearly 400 types of graphic files and convert any of these to more than 50 formats. It displays images very quickly and these may be viewed in full screen, as slideshows or as thumbnails. It's quite capable at processing images, too; you can rotate, crop, resize, adjust brightness and color, apply filters or effects, create a web page and much more. … A heavyweight champion. 

Best Free High Dynamic Range (HDR) Editor

Picturenaut "provides (all automatically) image alignment, exposure correction, color balancing, noise level compensation, and derivation of the camera curve from the source images. It supports most formats … As a modular piece of software, its most important functions can all be accessed from a command line. The downside is that you cannot alter the alignment of the image manually, but I have done tests on auto alignments and Picturenaut came out the best.  If you are looking for straightforward images without excessive tone mapping this has to be your top software."

Best Free Windows 64-bit Digital Image Stitcher

Microsoft ICE has "four modes of camera motion to stitch your sequence of images, three fixed and one that you can adjust the distortion and that the 'Rotation motion'. When in this mode just click the 3D icon on the top taskbar, where you can tilt, zoom in and out. When you are happy with your construction then you can leave the cropping to another imaging software or auto crop. The finished panoramic image is exported into JPG, BMP, TIFF, PNG, HD Photo image, Adobe Photoshop, HD View Tileset and Deep Zoom Tileset." 

Best Free Windows 64-bit Vector Graphics Editor

Inkscape "uses W3C standard Scalable Vector Graphics (SVG) file format. Supported SVG features include shapes, paths, text, markers, clones, alpha blending, transforms, gradients, patterns, and grouping. Inkscape also supports Creative Commons meta-data, node editing, layers, complex path operations, bitmap tracing, text-on-path, flowed text, direct XML editing, and more. It imports formats such as JPEG, PNG, TIFF, and others and exports PNG as well as multiple vector-based formats."
Inkscape "doesn't yet support SVG filter effects, animation, and SVG fonts. It is, however, totally usable. That usability is enhanced by an excellent user interface and the impressive set of tutorials"

Best Free Windows 64-bit Flow Charter and Diagrammer

yWorks develops Web-centric applications such as yEd Graphic Editor which is a Java Swing application. It runs as a native 64-bit application if you have the 64-bit Java Runtime Environment (JRE). I recommend yEd for its powerful automation features which are well presented in yWork's Flash video "yEd in 90 seconds". If you watched the video, then you've seen yEd's magical ability to import Excel data and automatically generate a diagram. It can use any of several layout types to arrange a complex flow chart or network diagram. If you need this then you won't be so concerned that other products are easier to use for basic editing and basic diagrams.
However, yEd is not as powerful as it appears in the video. All the example diagrams are not convoluted so they were able to be arranged flat without overlapping lines, something that never happens with my diagrams. If you are a serious diagrammer then you will also want to augment yEd's limited range of node types. yEd has symbols for Entity Relationship Models (ERM), Business Process Model and Notation (BPMN), Unified Modeling Language (UML) and the good old flow charts (but without sort, merge, logical AND and OR). Symbol sets are also provided for swim lanes and grouping. You can create custom symbols by importing bit-maps (PNG, JPG), vector graphics (SVG) and some Visio Shapes but within yEd they have few if any customizations. For example, they usually won't be able to change colour. Development is continuing so I expect to see future improvements in this area.

Best Free Windows 64-bit Image Optimizer

RIOT (Radical Image Optimization Tool) is simple to use. It makes your images smaller in size by resizing or compressing.This is a useful feature for optimizing web images but it just as useful for images included in other documents. RIOT uses a dual pane view to show the original and the optimized image. You can also toggle the images in either pane (in-place compare) so you can more easily compare the changes.
The steps are simple. Open an image file which can be bitmap files including Adobe Photoshop PSD files, popular HDR formats and RAW camera images. RIOT automatically reduces the file size. You then select  the output file type (JPEG, GIF, PNG), adjust the image, and set your options. You can also select a filesize for RIOT to aim for. Finally, save the image.