83 lines
2.5 KiB
Go
83 lines
2.5 KiB
Go
package artist
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import "image"
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// Side represents one side of a rectangle.
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type Side int; const (
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SideTop Side = iota
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SideRight
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SideBottom
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SideLeft
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)
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// Inset represents an inset amount for all four sides of a rectangle. The top
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// side is at index zero, the right at index one, the bottom at index two, and
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// the left at index three. These values may be negative.
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type Inset [4]int
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// I allows you to create an inset in a CSS-ish way:
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//
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// - One argument: all sides are set to this value
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// - Two arguments: the top and bottom sides are set to the first value, and
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// the left and right sides are set to the second value.
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// - Three arguments: the top side is set by the first value, the left and
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// right sides are set by the second vaue, and the bottom side is set by the
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// third value.
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// - Four arguments: each value corresponds to a side.
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//
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// This function will panic if an argument count that isn't one of these is
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// given.
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func I (sides ...int) Inset {
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switch len(sides) {
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case 1: return Inset { sides[0], sides[0], sides[0], sides[0] }
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case 2: return Inset { sides[0], sides[1], sides[0], sides[1] }
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case 3: return Inset { sides[0], sides[1], sides[2], sides[1] }
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case 4: return Inset { sides[0], sides[1], sides[2], sides[3] }
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default: panic("I: illegal argument count.")
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}
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}
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// Apply returns the given rectangle, shrunk on all four sides by the given
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// inset. If a measurment of the inset is negative, that side will instead be
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// expanded outward. If the rectangle's dimensions cannot be reduced any
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// further, an empty rectangle near its center will be returned.
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func (inset Inset) Apply (bigger image.Rectangle) (smaller image.Rectangle) {
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smaller = bigger
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if smaller.Dx() < inset[3] + inset[1] {
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smaller.Min.X = (smaller.Min.X + smaller.Max.X) / 2
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smaller.Max.X = smaller.Min.X
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} else {
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smaller.Min.X += inset[3]
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smaller.Max.X -= inset[1]
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}
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if smaller.Dy() < inset[0] + inset[2] {
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smaller.Min.Y = (smaller.Min.Y + smaller.Max.Y) / 2
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smaller.Max.Y = smaller.Min.Y
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} else {
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smaller.Min.Y += inset[0]
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smaller.Max.Y -= inset[2]
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}
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return
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}
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// Inverse returns a negated version of the inset.
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func (inset Inset) Inverse () (prime Inset) {
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return Inset {
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inset[0] * -1,
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inset[1] * -1,
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inset[2] * -1,
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inset[3] * -1,
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}
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}
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// Horizontal returns the sum of SideRight and SideLeft.
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func (inset Inset) Horizontal () int {
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return inset[SideRight] + inset[SideLeft]
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}
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// Vertical returns the sum of SideTop and SideBottom.
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func (inset Inset) Vertical () int {
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return inset[SideTop] + inset[SideBottom]
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}
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