examples/

README

Examples

Five standalone programs, each rendering a PNG into examples/out/. Run one with:

go run ./examples/blendmodes
go run ./examples/gradients
go run ./examples/effects
go run ./examples/paths
go run ./examples/showcase

Or render them all:

for d in blendmodes gradients effects paths showcase; do go run ./examples/$d; done

internal/demo holds the shared helpers (PNG saving, solid and checker fills, and the rounded-rect, star, and pentagram path builders).

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Showcase

showcase/main.go → out/showcase.png

A single poster that combines most of the library at once. Layers, bottom to top:

1. Background a diagonal linear gradient from deep blue to magenta.
2. Glow blobs three soft circles composited with the Screen blend mode at half opacity, for ambient colored light.
3. Badge a disc masked from a solid fill, carrying a drop shadow, a gradient overlay (orange to pink), a bevel, and a white outer stroke.
4. Emblem a gold star masked from a solid fill, with an outer glow, a drop shadow, and a bevel.
5. Panel a rounded card with a drop shadow, a gradient overlay, an inner shadow, and a thin inside stroke.

It also exercises vector masks, a pass-through root group, and the fixed effect-stacking order.

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Blend modes

blendmodes/main.go → out/blendmodes.png

Every cell blends the same two inputs. The backdrop is a horizontal rainbow and the overlay is a vertical ramp (white to purple to black):

Backdrop	Overlay

Each cell composites the overlay over the backdrop with one blend mode:

The formulas come from ISO 32000-2 (the PDF spec) section 11.3.5. Cells are in blend.Mode iota order, left to right, top to bottom:

Position	Mode	Category	What it does
Row 1, col 1	Normal	—	Source replaces the backdrop, weighted by alpha. No color interaction
Row 1, col 2	Multiply	Darkening	Multiplies channels. Always darkens, white is neutral. Like stacked transparencies
Row 1, col 3	Screen	Lightening	Inverse-multiply. Always lightens, black is neutral. Like projected light
Row 1, col 4	Overlay	Contrast	Multiplies the dark areas and screens the light ones, keyed on the backdrop. Boosts contrast
Row 2, col 1	Soft Light	Contrast	A gentle dodge or burn depending on the source, like a diffuse spotlight
Row 2, col 2	Hard Light	Contrast	Overlay with the operands swapped, keyed on the source. Harsh contrast
Row 2, col 3	Color Dodge	Lightening	Brightens the backdrop to reflect the source. Produces blown-out highlights
Row 2, col 4	Color Burn	Darkening	Darkens the backdrop to reflect the source. Produces crushed shadows
Row 3, col 1	Darken	Darkening	Keeps the darker of backdrop and source, per channel
Row 3, col 2	Lighten	Lightening	Keeps the lighter of backdrop and source, per channel
Row 3, col 3	Difference	Comparative	Absolute difference of the two. Identical colors cancel to black
Row 3, col 4	Exclusion	Comparative	Like Difference but lower contrast, mid-grays stay gray
Row 4, col 1	Hue	Non-separable	Source hue with the backdrop's saturation and luminance
Row 4, col 2	Saturation	Non-separable	Source saturation with the backdrop's hue and luminance
Row 4, col 3	Color	Non-separable	Source hue and saturation with the backdrop's luminance. Classic tinting
Row 4, col 4	Luminosity	Non-separable	Source luminance with the backdrop's hue and saturation

The four non-separable modes (Row 4) act on the whole RGB triple at once rather than channel by channel, using the Lum/Sat/SetLum/SetSat helpers from the spec.

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Gradients

gradients/main.go → out/gradients.png

The five gradient geometries plus a transparency demo. Every gradient is multi-stop with an independent color and opacity per stop, interpolated in sRGB to match Photoshop and converted to linear light for compositing. Cells left to right, top to bottom:

Position	Type	What it does
Row 1, col 1	Linear	Color runs along the axis from P0 to P1
Row 1, col 2	Radial	Concentric rings from a center, the radius set by |P1-P0|
Row 1, col 3	Angle (conic)	Sweeps the stops around the center by angle
Row 2, col 1	Reflected	A linear gradient mirrored about its start point
Row 2, col 2	Diamond	Square contours rotated to the axis, a Chebyshev-distance field
Row 2, col 3	Opacity fade	One color fading from opaque to transparent, shown over a checkerboard so the transparency is visible

Each type also supports a spread mode (Pad, Repeat, Reflect) for what happens outside the [0,1] parameter range, not shown here (all use Pad).

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Effects

effects/main.go → out/effects.png

The eight non-destructive layer styles, each applied to a rounded-rectangle badge. Glow cells use a dark backdrop so the glow reads. Cells left to right, top to bottom:

Position	Effect	What it does
Row 1, col 1	Drop Shadow	An offset, blurred copy of the layer's alpha behind it. Multiply by default
Row 1, col 2	Inner Shadow	Darkness inside the top edges, as if the shape were recessed. Multiply
Row 1, col 3	Outer Glow	Color radiating outward from the edge, behind the layer. Screen by default
Row 1, col 4	Inner Glow	Color radiating inward from the edge, clipped to the shape. Screen
Row 2, col 1	Color Overlay	A flat color filling the shape
Row 2, col 2	Gradient Overlay	A gradient field clipped to the shape
Row 2, col 3	Stroke	An outline band along the alpha edge, aligned inside, outside, or centered (outside here)
Row 2, col 4	Bevel & Emboss	A lit 3D relief derived from the alpha height field, split into a highlight (Screen) and a shadow (Multiply)

Shadows and outer glow render behind the layer, everything else renders in front. Effects are always composited in Photoshop's fixed stacking order regardless of the order you list them, so the same set always produces the same result. Bevel & emboss is close-and-configurable rather than pixel-exact, by design (it is the one effect with no clean public spec).

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Paths

paths/main.go → out/paths.png

Fill and stroke features drawn straight onto one buffer, top to bottom:

• Stroke caps (row 1) how open ends are terminated: Butt (flush with the endpoint), Round (a semicircle past the end), Square (a flat extension of half the stroke width).
• Stroke joins (row 2) how corners connect: Miter (extended to a sharp point, subject to a miter limit), Round (an arc), Bevel (a flat chamfer).
• Dashes (row 3) an on/off dash pattern, here with round caps on each dash.
• Fill rules (row 4, left and center) the same self-intersecting pentagram filled two ways: NonZero (winding number, solid center) and EvenOdd (crossing parity, hollow center pentagon).
• Bezier (row 4, right) chained cubic curves stroked with a round cap and join.

Stroking is the piece missing from the standard library's vector rasterizer, so this is the part of path with no off-the-shelf Go equivalent.