GO IMAGE FILTERING TOOLKIT (GIFT)

Package gift provides a set of useful image processing filters.

Pure Go. No external dependencies outside of the Go standard library.

INSTALLATION / UPDATING

go get -u github.com/disintegration/gift

DOCUMENTATION

http://godoc.org/github.com/disintegration/gift

QUICK START

// 1. Create a new GIFT and add some filters:
g := gift.New(
    gift.Resize(800, 0, gift.LanczosResampling),
    gift.UnsharpMask(1.0, 1.0, 0.0),
)

// 2. Create a new image of the corresponding size.
// dst is a new target image, src is the original image
dst := image.NewRGBA(g.Bounds(src.Bounds()))

// 3. Use Draw func to apply the filters to src and store the result in dst:
g.Draw(dst, src)

USAGE

To create a sequence of filters, the New function is used:

g := gift.New(
   gift.Grayscale(),
   gift.Contrast(10),
)

Filters also can be added using the Add method:

g.Add(GaussianBlur(2)) 

The Bounds method takes the bounds of the source image and returns appropriate bounds for the destination image to fit the result (for example, after using Resize or Rotate filters).

dst := image.NewRGBA(g.Bounds(src.Bounds()))

There are two methods available to apply these filters to an image:

• Draw applies all the added filters to the src image and outputs the result to the dst image starting from the top-left corner (Min point).

g.Draw(dst, src)

• DrawAt provides more control. It outputs the filtered src image to the dst image at the specified position using the specified image composition operator. This example is equivalent to the previous:

g.DrawAt(dst, src, dst.Bounds().Min, gift.CopyOperator)

Two image composition operators are supported by now:

• CopyOperator - Replaces pixels of the dst image with pixels of the filtered src image. This mode is used by the Draw method.
• OverOperator - Places the filtered src image on top of the dst image. This mode makes sence if the filtered src image has transparent areas.

Empty filter list can be used to create a copy of an image or to paste one image to another. For example:

// Create a new image with dimensions of bgImage
dstImage := image.NewNRGBA(bgImage.Bounds())
// Copy the bgImage to the dstImage.
gift.New().Draw(dstImage, bgImage)
// Draw the fgImage over the dstImage at the (100, 100) position.
gift.New().DrawAt(dstImage, fgImage, image.Pt(100, 100), gift.OverOperator)

SUPPORTED FILTERS

• Transformations

  • Crop(rect image.Rectangle)
  • CropToSize(width, height int, anchor Anchor)
  • FlipHorizontal()
  • FlipVertical()
  • Resize(width, height int, resampling Resampling)
  • ResizeToFill(width, height int, resampling Resampling, anchor Anchor)
  • ResizeToFit(width, height int, resampling Resampling)
  • Rotate(angle float32, backgroundColor color.Color, interpolation Interpolation)
  • Rotate180()
  • Rotate270()
  • Rotate90()
  • Transpose()
  • Transverse()

• Adjustments & effects

  • Brightness(percentage float32)
  • ColorBalance(percentageRed, percentageGreen, percentageBlue float32)
  • ColorFunc(fn func(r0, g0, b0, a0 float32) (r, g, b, a float32))
  • Colorize(hue, saturation, percentage float32)
  • ColorspaceLinearToSRGB()
  • ColorspaceSRGBToLinear()
  • Contrast(percentage float32)
  • Convolution(kernel []float32, normalize, alpha, abs bool, delta float32)
  • Gamma(gamma float32)
  • GaussianBlur(sigma float32)
  • Grayscale()
  • Hue(shift float32)
  • Invert()
  • Maximum(ksize int, disk bool)
  • Mean(ksize int, disk bool)
  • Median(ksize int, disk bool)
  • Minimum(ksize int, disk bool)
  • Saturation(percentage float32)
  • Sepia(percentage float32)
  • Sigmoid(midpoint, factor float32)
  • Sobel()
  • UnsharpMask(sigma, amount, thresold float32)

FILTER EXAMPLES

Resize using lanczos resampling

gift.Resize(200, 0, gift.LanczosResampling)

Original image	Filtered image

Resize using linear resampling

gift.Resize(200, 0, gift.LinearResampling)

Original image	Filtered image

Resize to fit 160x160px bounding box

gift.ResizeToFit(160, 160, gift.LanczosResampling)

Original image	Filtered image

Resize to fill 160x160px rectangle, anchor: center

gift.ResizeToFill(160, 160, gift.LanczosResampling, gift.CenterAnchor)

Original image	Filtered image

Crop 90, 90 - 250, 250

gift.Crop(image.Rect(90, 90, 250, 250))

Original image	Filtered image

Crop to size 160x160px, anchor: center

gift.CropToSize(160, 160, gift.CenterAnchor)

Original image	Filtered image

Rotate 90 degrees

gift.Rotate90()

Original image	Filtered image

Rotate 180 degrees

gift.Rotate180()

Original image	Filtered image

Rotate 270 degrees

gift.Rotate270()

Original image	Filtered image

Rotate 30 degrees, white background, cubic interpolation

gift.Rotate(30, color.White, gift.CubicInterpolation)

Original image	Filtered image

Flip horizontal

gift.FlipHorizontal()

Original image	Filtered image

Flip vertical

gift.FlipVertical()

Original image	Filtered image

Transpose

gift.Transpose()

Original image	Filtered image

Transverse

gift.Transverse()

Original image	Filtered image

Contrast +30%

gift.Contrast(30)

Original image	Filtered image

Contrast -30%

gift.Contrast(-30)

Original image	Filtered image

Brightness +30%

gift.Brightness(30)

Original image	Filtered image

Brightness -30%

gift.Brightness(-30)

Original image	Filtered image

Saturation +50%

gift.Saturation(50)

Original image	Filtered image

Saturation -50%

gift.Saturation(-50)

Original image	Filtered image

Hue +45

gift.Hue(45)

Original image	Filtered image

Hue -45

gift.Hue(-45)

Original image	Filtered image

Sigmoid 0.5, 5.0

gift.Sigmoid(0.5, 5.0)

Original image	Filtered image

Gamma correction = 0.5

gift.Gamma(0.5)

Original image	Filtered image

Gamma correction = 1.5

gift.Gamma(1.5)

Original image	Filtered image

Gaussian blur, sigma=1.0

gift.GaussianBlur(1.0)

Original image	Filtered image

Unsharp mask, sigma=1.0, amount=1.5, thresold=0.0

gift.UnsharpMask(1.0, 1.5, 0.0)

Original image	Filtered image

Grayscale

gift.Grayscale()

Original image	Filtered image

Sepia, 100%

gift.Sepia(100)

Original image	Filtered image

Invert

gift.Invert()

Original image	Filtered image

Colorize, blue, saturation=50%

gift.Colorize(240, 50, 100)

Original image	Filtered image

Color balance, +20% red, -20% green

gift.ColorBalance(20, -20, 0)

Original image	Filtered image

Color function

gift.ColorFunc(
    func(r0, g0, b0, a0 float32) (r, g, b, a float32) {
        r = 1 - r0   // invert the red channel
        g = g0 + 0.1 // shift the green channel by 0.1
        b = 0        // set the blue channel to 0
        a = a0       // preserve the alpha channel
        return
    },
)

Original image	Filtered image

Local mean, disc shape, size=5

gift.Mean(5, true)

Original image	Filtered image

Local median, disc shape, size=5

gift.Median(5, true)

Original image	Filtered image

Local minimum, disc shape, size=5

gift.Minimum(5, true)

Original image	Filtered image

Local maximum, disc shape, size=5

gift.Maximum(5, true)

Original image	Filtered image

Convolution matrix - Emboss

gift.Convolution(
    []float32{
        -1, -1, 0,
        -1, 1, 1,
        0, 1, 1,
    },
    false, false, false, 0.0,
)

Original image	Filtered image

Convolution matrix - Edge detection

gift.Convolution(
    []float32{
        -1, -1, -1,
        -1, 8, -1,
        -1, -1, -1,
    },
    false, false, false, 0.0,
)

Original image	Filtered image

Sobel operator

gift.Sobel()

Original image	Filtered image