grokify/mogo

package imageutil

import (
    "image"
    "image/color"
    "image/draw"
)

// PaintBorder colorizes a border of size `width` in the existing
// canvas, overwriting any colors in that space.
func PaintBorder(img draw.Image, clr color.Color, width uint) {
    if img == nil || width == 0 {
        return
    }
    PaintColor(img, clr, RectangleBorderXMin(img.Bounds(), width))
    PaintColor(img, clr, RectangleBorderXMax(img.Bounds(), width))
    PaintColor(img, clr, RectangleBorderYMin(img.Bounds(), width))
    PaintColor(img, clr, RectangleBorderYMax(img.Bounds(), width))
}

func RectangleBorderXMin(rect image.Rectangle, pixels uint) image.Rectangle {
    maxY := rect.Min.Y + int(pixels)
    if maxY > rect.Max.Y {
        maxY = rect.Max.Y
    }
    return image.Rect(rect.Min.X, rect.Min.Y, rect.Max.X, maxY)
}

func RectangleBorderXMax(rect image.Rectangle, pixels uint) image.Rectangle {
    minY := rect.Max.Y - int(pixels)
    if minY < rect.Min.Y {
        minY = rect.Min.Y
    }
    return image.Rect(rect.Min.X, minY, rect.Max.X, rect.Max.Y)
}

func RectangleBorderYMin(rect image.Rectangle, pixels uint) image.Rectangle {
    maxX := rect.Min.X + int(pixels)
    if maxX > rect.Max.X {
        maxX = rect.Max.X
    }
    return image.Rect(rect.Min.X, rect.Min.Y, maxX, rect.Max.Y)
}

func RectangleBorderYMax(rect image.Rectangle, pixels uint) image.Rectangle {
    minX := rect.Max.X - int(pixels)
    if minX < rect.Min.X {
        minX = rect.Min.X
    }
    return image.Rect(minX, rect.Min.Y, rect.Max.X, rect.Max.Y)
}