nearest.go

/*
Copyright (c) 2014, Charlie Vieth <charlie.vieth@gmail.com>

Permission to use, copy, modify, and/or distribute this software for any purpose
with or without fee is hereby granted, provided that the above copyright notice
and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
THIS SOFTWARE.
*/

package resize

import "image"

func floatToUint8(x float32) uint8 {
	// Nearest-neighbor values are always
	// positive no need to check lower-bound.
	if x > 0xfe {
		return 0xff
	}
	return uint8(x)
}

func floatToUint16(x float32) uint16 {
	if x > 0xfffe {
		return 0xffff
	}
	return uint16(x)
}

func nearestGeneric(in image.Image, out *image.RGBA64, scale float64, coeffs []bool, offset []int, filterLength int) {
	newBounds := out.Bounds()
	maxX := in.Bounds().Dx() - 1

	for x := newBounds.Min.X; x < newBounds.Max.X; x++ {
		for y := newBounds.Min.Y; y < newBounds.Max.Y; y++ {
			var rgba [4]float32
			var sum float32
			start := offset[y]
			ci := y * filterLength
			for i := 0; i < filterLength; i++ {
				if coeffs[ci+i] {
					xi := start + i
					switch {
					case xi < 0:
						xi = 0
					case xi >= maxX:
						xi = maxX
					}
					r, g, b, a := in.At(xi+in.Bounds().Min.X, x+in.Bounds().Min.Y).RGBA()
					rgba[0] += float32(r)
					rgba[1] += float32(g)
					rgba[2] += float32(b)
					rgba[3] += float32(a)
					sum++
				}
			}

			offset := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*8
			value := floatToUint16(rgba[0] / sum)
			out.Pix[offset+0] = uint8(value >> 8)
			out.Pix[offset+1] = uint8(value)
			value = floatToUint16(rgba[1] / sum)
			out.Pix[offset+2] = uint8(value >> 8)
			out.Pix[offset+3] = uint8(value)
			value = floatToUint16(rgba[2] / sum)
			out.Pix[offset+4] = uint8(value >> 8)
			out.Pix[offset+5] = uint8(value)
			value = floatToUint16(rgba[3] / sum)
			out.Pix[offset+6] = uint8(value >> 8)
			out.Pix[offset+7] = uint8(value)
		}
	}
}

func nearestRGBA(in *image.RGBA, out *image.RGBA, scale float64, coeffs []bool, offset []int, filterLength int) {
	newBounds := out.Bounds()
	maxX := in.Bounds().Dx() - 1

	for x := newBounds.Min.X; x < newBounds.Max.X; x++ {
		row := in.Pix[x*in.Stride:]
		for y := newBounds.Min.Y; y < newBounds.Max.Y; y++ {
			var rgba [4]float32
			var sum float32
			start := offset[y]
			ci := y * filterLength
			for i := 0; i < filterLength; i++ {
				if coeffs[ci+i] {
					xi := start + i
					switch {
					case xi < 0:
						xi = 0
					case xi >= maxX:
						xi = 4 * maxX
					default:
						xi *= 4
					}
					rgba[0] += float32(row[xi+0])
					rgba[1] += float32(row[xi+1])
					rgba[2] += float32(row[xi+2])
					rgba[3] += float32(row[xi+3])
					sum++
				}
			}

			xo := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*4
			out.Pix[xo+0] = floatToUint8(rgba[0] / sum)
			out.Pix[xo+1] = floatToUint8(rgba[1] / sum)
			out.Pix[xo+2] = floatToUint8(rgba[2] / sum)
			out.Pix[xo+3] = floatToUint8(rgba[3] / sum)
		}
	}
}

func nearestRGBA64(in *image.RGBA64, out *image.RGBA64, scale float64, coeffs []bool, offset []int, filterLength int) {
	newBounds := out.Bounds()
	maxX := in.Bounds().Dx() - 1

	for x := newBounds.Min.X; x < newBounds.Max.X; x++ {
		row := in.Pix[x*in.Stride:]
		for y := newBounds.Min.Y; y < newBounds.Max.Y; y++ {
			var rgba [4]float32
			var sum float32
			start := offset[y]
			ci := y * filterLength
			for i := 0; i < filterLength; i++ {
				if coeffs[ci+i] {
					xi := start + i
					switch {
					case xi < 0:
						xi = 0
					case xi >= maxX:
						xi = 8 * maxX
					default:
						xi *= 8
					}
					rgba[0] += float32(uint16(row[xi+0])<<8 | uint16(row[xi+1]))
					rgba[1] += float32(uint16(row[xi+2])<<8 | uint16(row[xi+3]))
					rgba[2] += float32(uint16(row[xi+4])<<8 | uint16(row[xi+5]))
					rgba[3] += float32(uint16(row[xi+6])<<8 | uint16(row[xi+7]))
					sum++
				}
			}

			xo := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*8
			value := floatToUint16(rgba[0] / sum)
			out.Pix[xo+0] = uint8(value >> 8)
			out.Pix[xo+1] = uint8(value)
			value = floatToUint16(rgba[1] / sum)
			out.Pix[xo+2] = uint8(value >> 8)
			out.Pix[xo+3] = uint8(value)
			value = floatToUint16(rgba[2] / sum)
			out.Pix[xo+4] = uint8(value >> 8)
			out.Pix[xo+5] = uint8(value)
			value = floatToUint16(rgba[3] / sum)
			out.Pix[xo+6] = uint8(value >> 8)
			out.Pix[xo+7] = uint8(value)
		}
	}
}

func nearestGray(in *image.Gray, out *image.Gray, scale float64, coeffs []bool, offset []int, filterLength int) {
	newBounds := out.Bounds()
	maxX := in.Bounds().Dx() - 1

	for x := newBounds.Min.X; x < newBounds.Max.X; x++ {
		row := in.Pix[x*in.Stride:]
		for y := newBounds.Min.Y; y < newBounds.Max.Y; y++ {
			var gray float32
			var sum float32
			start := offset[y]
			ci := y * filterLength
			for i := 0; i < filterLength; i++ {
				if coeffs[ci+i] {
					xi := start + i
					switch {
					case xi < 0:
						xi = 0
					case xi >= maxX:
						xi = maxX
					}
					gray += float32(row[xi])
					sum++
				}
			}

			offset := (y-newBounds.Min.Y)*out.Stride + (x - newBounds.Min.X)
			out.Pix[offset] = floatToUint8(gray / sum)
		}
	}
}

func nearestGray16(in *image.Gray16, out *image.Gray16, scale float64, coeffs []bool, offset []int, filterLength int) {
	newBounds := out.Bounds()
	maxX := in.Bounds().Dx() - 1

	for x := newBounds.Min.X; x < newBounds.Max.X; x++ {
		row := in.Pix[x*in.Stride:]
		for y := newBounds.Min.Y; y < newBounds.Max.Y; y++ {
			var gray float32
			var sum float32
			start := offset[y]
			ci := y * filterLength
			for i := 0; i < filterLength; i++ {
				if coeffs[ci+i] {
					xi := start + i
					switch {
					case xi < 0:
						xi = 0
					case xi >= maxX:
						xi = 2 * maxX
					default:
						xi *= 2
					}
					gray += float32(uint16(row[xi+0])<<8 | uint16(row[xi+1]))
					sum++
				}
			}

			offset := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*2
			value := floatToUint16(gray / sum)
			out.Pix[offset+0] = uint8(value >> 8)
			out.Pix[offset+1] = uint8(value)
		}
	}
}