PaintTool SAI is a drawing and painting application for Windows, built for creating digital illustrations with a pen tablet. It combines pressure-sensitive painting with separate linework layers, so freehand brush marks and editable outlines can form parts of the same canvas.
Pen strokes
PaintTool SAI accepts pressure input from a compatible drawing tablet and produces anti-aliased strokes, smoothing their edges against the surrounding pixels. Its stroke stabilizer provides an additional control over drawing response. Stabilization can be set from the quick bar or for individual tools; the stronger S-series settings introduce a delay between pen movement and the drawn stroke.
Brush customization includes bristle shapes such as round and flat, along with brush and paper textures. Custom brushes can be saved for reuse, keeping a chosen tool configuration available for later drawings.
Choosing colors
The color wheel and sliders provide ways to choose paint colors. HSV and HLS modes express color through hue and related brightness or lightness controls, while SAI’s V-HSV mode changes how colors transition as the value setting decreases. A color picker can sample existing artwork, with its sampling source selected in the tool panel. Saved swatches hold colors that need to recur across the illustration.
PaintTool SAI’s linework layers
Dedicated linework layers keep strokes available for further editing instead of immediately treating them as ordinary painted pixels. Pen, Curve and Line tools provide different ways to construct outlines. A pressure tool adjusts pressure along linework, allowing the stroke’s emphasis to be revised after drawing.
PaintTool SAI can copy linework strokes and rasterize a linework layer. Rasterizing turns that layer into pixel artwork for painting operations. Keeping linework separate from color layers also lets the outlines remain visible while the paint beneath them changes.
Paint layers
Layer sets organize parts of an illustration, and visibility controls let you inspect one layer or a group without deleting other work. Preserve Opacity confines changes to the layer’s existing painted area. Clipping groups use the underlying layer’s coverage to restrict the visible paint above it, allowing shading to follow an established silhouette.
Composition modes change how those layers interact. Shade, Luminosity and Overlay offer different treatments for darkening, lightening and combining colors. PaintTool SAI calculates composition with 16-bit ARGB channels, keeping color and transparency information in its internal painting calculations.
Merge Visible Layers combines the visible artwork while retaining hidden layers. Flatten Image collapses the image’s layered structure.
File formats and licensing
The native SAI format stores working artwork, while PSD support provides a route for exchanging layered images with other graphics software. PaintTool SAI also handles common bitmap formats including JPEG, PNG, BMP and TGA. Transparent PNG output allows an illustration to retain an empty background rather than embedding it in a solid rectangle.
The application is paid software with a fully functional trial. When the trial ends, opening and saving files are disabled until a software license is applied.
