The most important features chalk currently has to offer, are:
Plugins: Chalk is extensible through plugins. There are tools, colorspaces, paint operations, filters and kpart-based user interface plugins.
Scriptable: chalk is scriptable in Python and Ruby using Kross, the cross language scripting engine that originated in Kexi. The scripting is compatible with PyQt/KDE and Korundum for adding GUI items, such as dialog boxes.
Color models: chalk uses lcms for a dependable color workflow using icc profiles for importing, exporting, selecting paint colors, printing, cutting and pasting. 8, 16, and 32 bit colorspaces are available (RGB, CMYK, L*a*b*, ...) and colors can be selected from a color wheel, rgb or grayscale sliders or with a palette.
Editing and viewing: Unlimited undo and redo are available. You can cut, copy and paste between lagers and images, with conversion through icc profiles if this is necessary. OpenGL is supported for display. The view can be made fullscreen and can be split. Rulers are available, the image can be zoomed, and for maximizing the workspace all palette windows can be hidden in one go. Also a histogram palette is available.
Images and layers: Layers and entire images can be mirrored, sheared, rotated and scaled, converted between colorspaces, and layers in different colorspaces can be merged. An image can be separated into colorspace channels.
Layers: Layers can be added, removed, grouped, locked, made (in)visible, and re-ordered. Adjustment layers (layers which perform a filter function) can be added as well. A layer can be saved as a separate image and its colorspace can be changed.
Tools: Through the innovative paintOp plugin system, all painting tools (brush, ellipse, line, etc.) can paint aliased, anti-aliased, erase, airbrush and more.
Filters: chalk can multithread the operation of some filters. Filters can be previewed in the filter gallery. Available filters include color adjustment, sharpen or blur, emboss, raindrops, and more.
Brushes: The GIMP brush shapes can be used, both colored and grayscale brushes and pipe brushes. Custom brushes can be created, even from entire layers or images. Colored brushes can also be used as masks.
One of the most distinguishing features in chalk is its color management. If you put two screens side to side, you will notice that there is often a lot of difference in the way they display colors. Even white, especially white, is often not the same thing at all. On one screen it can be a dirty yellow, on another screen a sickly bluish. Very seldom is it a creamy milk-white. The same holds, unfortunately, for scanners, printers and digital cameras. So, if you want to see the right colors on screen and on paper, being the colors that you saw when taking your snapshot, you will have to compensate.
chalk can do this for you: in chalk, a color is (almost) never just a set of numbers, one for each color channel; it is a set of numbers with information attached. And that extra information is contained in a profile: your image has a profile, your scanner has a profile, your camera should have a profile and your screen has a profile. When passing information from your image to your screen, the profiles are checked and the correct color is computed. This may cause a little slowness, now and then, but the result is that you can work with colors, instead of almost meaningless RGB triplets.
Available colorspaces are: 8 bit/channel RGB, CMYK, grayscale and wet watercolors, 16 bit/channel RGB, CMYK, grayscale and L*a*b*, “half” RGB, and 32 bit float RGB (HDR) and LMS.
chalk currently supports the following image formats, both for importing and exporting, apart from its own: PNG, TIFF, JPEG, Dicom, XCF, PSD, GIF, BMP, XPM, Targa, RGB, and OpenEXR. Additionally, chalk can import ICO files. PSD (the Photoshop file format) is only supported up to version 6, from version 7 on, the Photoshop file format is closed.
Embedded icc profiles and exif information are preserved on export to supporting file formats. chalk's native file format stores icc and exif information.
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