| package imaging |
| |
| import ( |
| "image" |
| "image/color" |
| "math" |
| ) |
| |
| // Grayscale produces a grayscale version of the image. |
| func Grayscale(img image.Image) *image.NRGBA { |
| src := newScanner(img) |
| dst := image.NewNRGBA(image.Rect(0, 0, src.w, src.h)) |
| parallel(0, src.h, func(ys <-chan int) { |
| for y := range ys { |
| i := y * dst.Stride |
| src.scan(0, y, src.w, y+1, dst.Pix[i:i+src.w*4]) |
| for x := 0; x < src.w; x++ { |
| r := dst.Pix[i+0] |
| g := dst.Pix[i+1] |
| b := dst.Pix[i+2] |
| f := 0.299*float64(r) + 0.587*float64(g) + 0.114*float64(b) |
| y := uint8(f + 0.5) |
| dst.Pix[i+0] = y |
| dst.Pix[i+1] = y |
| dst.Pix[i+2] = y |
| i += 4 |
| } |
| } |
| }) |
| return dst |
| } |
| |
| // Invert produces an inverted (negated) version of the image. |
| func Invert(img image.Image) *image.NRGBA { |
| src := newScanner(img) |
| dst := image.NewNRGBA(image.Rect(0, 0, src.w, src.h)) |
| parallel(0, src.h, func(ys <-chan int) { |
| for y := range ys { |
| i := y * dst.Stride |
| src.scan(0, y, src.w, y+1, dst.Pix[i:i+src.w*4]) |
| for x := 0; x < src.w; x++ { |
| dst.Pix[i+0] = 255 - dst.Pix[i+0] |
| dst.Pix[i+1] = 255 - dst.Pix[i+1] |
| dst.Pix[i+2] = 255 - dst.Pix[i+2] |
| i += 4 |
| } |
| } |
| }) |
| return dst |
| } |
| |
| // AdjustContrast changes the contrast of the image using the percentage parameter and returns the adjusted image. |
| // The percentage must be in range (-100, 100). The percentage = 0 gives the original image. |
| // The percentage = -100 gives solid gray image. |
| // |
| // Examples: |
| // |
| // dstImage = imaging.AdjustContrast(srcImage, -10) // decrease image contrast by 10% |
| // dstImage = imaging.AdjustContrast(srcImage, 20) // increase image contrast by 20% |
| // |
| func AdjustContrast(img image.Image, percentage float64) *image.NRGBA { |
| percentage = math.Min(math.Max(percentage, -100.0), 100.0) |
| lut := make([]uint8, 256) |
| |
| v := (100.0 + percentage) / 100.0 |
| for i := 0; i < 256; i++ { |
| if 0 <= v && v <= 1 { |
| lut[i] = clamp((0.5 + (float64(i)/255.0-0.5)*v) * 255.0) |
| } else if 1 < v && v < 2 { |
| lut[i] = clamp((0.5 + (float64(i)/255.0-0.5)*(1/(2.0-v))) * 255.0) |
| } else { |
| lut[i] = uint8(float64(i)/255.0+0.5) * 255 |
| } |
| } |
| |
| return adjustLUT(img, lut) |
| } |
| |
| // AdjustBrightness changes the brightness of the image using the percentage parameter and returns the adjusted image. |
| // The percentage must be in range (-100, 100). The percentage = 0 gives the original image. |
| // The percentage = -100 gives solid black image. The percentage = 100 gives solid white image. |
| // |
| // Examples: |
| // |
| // dstImage = imaging.AdjustBrightness(srcImage, -15) // decrease image brightness by 15% |
| // dstImage = imaging.AdjustBrightness(srcImage, 10) // increase image brightness by 10% |
| // |
| func AdjustBrightness(img image.Image, percentage float64) *image.NRGBA { |
| percentage = math.Min(math.Max(percentage, -100.0), 100.0) |
| lut := make([]uint8, 256) |
| |
| shift := 255.0 * percentage / 100.0 |
| for i := 0; i < 256; i++ { |
| lut[i] = clamp(float64(i) + shift) |
| } |
| |
| return adjustLUT(img, lut) |
| } |
| |
| // AdjustGamma performs a gamma correction on the image and returns the adjusted image. |
| // Gamma parameter must be positive. Gamma = 1.0 gives the original image. |
| // Gamma less than 1.0 darkens the image and gamma greater than 1.0 lightens it. |
| // |
| // Example: |
| // |
| // dstImage = imaging.AdjustGamma(srcImage, 0.7) |
| // |
| func AdjustGamma(img image.Image, gamma float64) *image.NRGBA { |
| e := 1.0 / math.Max(gamma, 0.0001) |
| lut := make([]uint8, 256) |
| |
| for i := 0; i < 256; i++ { |
| lut[i] = clamp(math.Pow(float64(i)/255.0, e) * 255.0) |
| } |
| |
| return adjustLUT(img, lut) |
| } |
| |
| // AdjustSigmoid changes the contrast of the image using a sigmoidal function and returns the adjusted image. |
| // It's a non-linear contrast change useful for photo adjustments as it preserves highlight and shadow detail. |
| // The midpoint parameter is the midpoint of contrast that must be between 0 and 1, typically 0.5. |
| // The factor parameter indicates how much to increase or decrease the contrast, typically in range (-10, 10). |
| // If the factor parameter is positive the image contrast is increased otherwise the contrast is decreased. |
| // |
| // Examples: |
| // |
| // dstImage = imaging.AdjustSigmoid(srcImage, 0.5, 3.0) // increase the contrast |
| // dstImage = imaging.AdjustSigmoid(srcImage, 0.5, -3.0) // decrease the contrast |
| // |
| func AdjustSigmoid(img image.Image, midpoint, factor float64) *image.NRGBA { |
| if factor == 0 { |
| return Clone(img) |
| } |
| |
| lut := make([]uint8, 256) |
| a := math.Min(math.Max(midpoint, 0.0), 1.0) |
| b := math.Abs(factor) |
| sig0 := sigmoid(a, b, 0) |
| sig1 := sigmoid(a, b, 1) |
| e := 1.0e-6 |
| |
| if factor > 0 { |
| for i := 0; i < 256; i++ { |
| x := float64(i) / 255.0 |
| sigX := sigmoid(a, b, x) |
| f := (sigX - sig0) / (sig1 - sig0) |
| lut[i] = clamp(f * 255.0) |
| } |
| } else { |
| for i := 0; i < 256; i++ { |
| x := float64(i) / 255.0 |
| arg := math.Min(math.Max((sig1-sig0)*x+sig0, e), 1.0-e) |
| f := a - math.Log(1.0/arg-1.0)/b |
| lut[i] = clamp(f * 255.0) |
| } |
| } |
| |
| return adjustLUT(img, lut) |
| } |
| |
| func sigmoid(a, b, x float64) float64 { |
| return 1 / (1 + math.Exp(b*(a-x))) |
| } |
| |
| // adjustLUT applies the given lookup table to the colors of the image. |
| func adjustLUT(img image.Image, lut []uint8) *image.NRGBA { |
| src := newScanner(img) |
| dst := image.NewNRGBA(image.Rect(0, 0, src.w, src.h)) |
| parallel(0, src.h, func(ys <-chan int) { |
| for y := range ys { |
| i := y * dst.Stride |
| src.scan(0, y, src.w, y+1, dst.Pix[i:i+src.w*4]) |
| for x := 0; x < src.w; x++ { |
| dst.Pix[i+0] = lut[dst.Pix[i+0]] |
| dst.Pix[i+1] = lut[dst.Pix[i+1]] |
| dst.Pix[i+2] = lut[dst.Pix[i+2]] |
| i += 4 |
| } |
| } |
| }) |
| return dst |
| } |
| |
| // AdjustFunc applies the fn function to each pixel of the img image and returns the adjusted image. |
| // |
| // Example: |
| // |
| // dstImage = imaging.AdjustFunc( |
| // srcImage, |
| // func(c color.NRGBA) color.NRGBA { |
| // // shift the red channel by 16 |
| // r := int(c.R) + 16 |
| // if r > 255 { |
| // r = 255 |
| // } |
| // return color.NRGBA{uint8(r), c.G, c.B, c.A} |
| // } |
| // ) |
| // |
| func AdjustFunc(img image.Image, fn func(c color.NRGBA) color.NRGBA) *image.NRGBA { |
| src := newScanner(img) |
| dst := image.NewNRGBA(image.Rect(0, 0, src.w, src.h)) |
| parallel(0, src.h, func(ys <-chan int) { |
| for y := range ys { |
| i := y * dst.Stride |
| src.scan(0, y, src.w, y+1, dst.Pix[i:i+src.w*4]) |
| for x := 0; x < src.w; x++ { |
| r := dst.Pix[i+0] |
| g := dst.Pix[i+1] |
| b := dst.Pix[i+2] |
| a := dst.Pix[i+3] |
| c := fn(color.NRGBA{r, g, b, a}) |
| dst.Pix[i+0] = c.R |
| dst.Pix[i+1] = c.G |
| dst.Pix[i+2] = c.B |
| dst.Pix[i+3] = c.A |
| i += 4 |
| } |
| } |
| }) |
| return dst |
| } |
