grokify/mogo

package imageutil

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

const (
    AlignTop    = "top"
    AlignCenter = "center"
    AlignBottom = "bottom"
    AlignLeft   = "left"
    AlignRight  = "right"
)

// Crop takes an image and crops it to the specified rectangle.
func Crop(src image.Image, retain image.Rectangle) image.Image {
    new := image.NewRGBA(retain)
    draw.Draw(new, new.Bounds(), src, retain.Min, draw.Over)
    return new
}

// CropX crops an image by its width horizontally.
func CropX(src image.Image, width uint, align string) image.Image {
    if int(width) >= src.Bounds().Dx() {
        return src
    }
    var xMin int
    switch strings.ToLower(strings.TrimSpace(align)) {
    case AlignLeft:
        xMin = src.Bounds().Min.X
    case AlignRight:
        xMin = src.Bounds().Max.X - int(width)
    default:
        xMin = (src.Bounds().Max.X - int(width)) / 2
    }
    return Crop(src, image.Rect(
        xMin,
        src.Bounds().Min.Y,
        xMin+int(width),
        src.Bounds().Max.Y))
}

// CropY crops an image by its height vertically.
func CropY(src image.Image, height uint, align string) image.Image {
    if int(height) >= src.Bounds().Dy() {
        return src
    }
    var yMin int
    switch strings.ToLower(strings.TrimSpace(align)) {
    case AlignTop:
        yMin = src.Bounds().Min.Y
    case AlignBottom:
        yMin = src.Bounds().Max.Y - int(height)
    default:
        yMin = (src.Bounds().Max.Y - int(height)) / 2
    }
    return Crop(src, image.Rect(
        src.Bounds().Min.X,
        yMin,
        src.Bounds().Max.X,
        yMin+int(height)))
}

// SquareLarger returns an image that is cropped to where the height and weight are equal
// to the larger of the source image.
func SquareLarger(src image.Image, bgcolor color.Color) image.Image {
    width := src.Bounds().Dx()
    height := src.Bounds().Dy()
    switch {
    case width > height:
        new := AddBackgroundColor(image.NewRGBA(image.Rect(0, 0, width, width)), bgcolor)
        draw.Draw(new, new.Bounds(), src, image.Point{
            Y: src.Bounds().Min.Y + ((height - width) / 2),
            X: src.Bounds().Min.X}, draw.Over)
        return new
    case width < height:
        new := AddBackgroundColor(image.NewRGBA(image.Rect(0, 0, height, height)), bgcolor)
        draw.Draw(new, new.Bounds(), src, image.Point{
            X: src.Bounds().Min.X + ((width - height) / 2),
            Y: src.Bounds().Min.Y}, draw.Over)
        return new
    default:
        return src
    }
}

// Square returns an image that is cropped to where the height and weight are equal to the smaller of the source image.
func Square(src image.Image) image.Image {
    width := src.Bounds().Dx()
    height := src.Bounds().Dy()
    switch {
    case width > height:
        return CropX(src, uint(height), AlignCenter)
    case width < height:
        return CropY(src, uint(width), AlignCenter)
    default:
        return src
    }
}