grokify/mogo

package imageutil

import (
    "image"
    "image/draw"
    "strings"
)

func Overlay(src, overlay image.Image, offset image.Point) image.Image {
    output := image.NewRGBA(src.Bounds())
    draw.Draw(output, src.Bounds(), src, image.Point{}, draw.Src)
    draw.Draw(output, overlay.Bounds().Add(offset), overlay, image.Point{}, draw.Src)
    return output
}

const (
    LocUpper      = "upper"
    LocMiddle     = "middle"
    LocLower      = "lower"
    LocLeft       = "left"
    LocCenter     = "center"
    LocRight      = "right"
    LocUpperLeft  = "upperleft"
    LocUpperRight = "upperright"
    LocLowerLeft  = "lowerleft"
    LocLowerRight = "lowerright"
)

func OverlayMore(src, overlay image.Image, overlayLocation string, padX, padY int) image.Image {
    return Overlay(src, overlay, OverlayOffset(src.Bounds(), overlay.Bounds(), overlayLocation, padX, padY))
}

func OverlayOffset(src, overlay image.Rectangle, overlayLocation string, padX, padY int) image.Point {
    pt := image.Point{}
    if strings.Contains(overlayLocation, LocUpper) {
        pt.Y = src.Min.Y + padY
    } else if strings.Contains(overlayLocation, LocLower) {
        pt.Y = src.Max.Y - overlay.Dy() - padY
    } else {
        pt.Y = src.Max.Y - ((src.Dy() - overlay.Dy()) / 2) + padY
    }
    if strings.Contains(overlayLocation, LocLeft) {
        pt.X = src.Min.X + padX
    } else if strings.Contains(overlayLocation, LocRight) {
        pt.X = src.Max.X - overlay.Dx() - padX
    } else {
        pt.X = src.Max.X - ((src.Dx() - overlay.Dx()) / 2) + padX
    }
    return pt
}

/*

func OverlayCenterYLeftAlign(src, overlay image.Image) image.Image {
    h1 := src.Bounds().Dy()
    h2 := overlay.Bounds().Dy()
    offset := image.Pt(0, (h1-h2)/2)
    return Overlay(src, overlay, offset)
}

func OverlayLowerLeft(src, overlay image.Image) image.Image {
    return Overlay(
        src, overlay,
        image.Pt(
            src.Bounds().Min.X,
            src.Bounds().Max.Y-overlay.Bounds().Dy()))
}

*/