Use bild library

cbconvert_image.go

@@ -0,0 +1,135 @@
+package cbconvert
+
+import (
+	"image"
+	"image/color"
+	"image/draw"
+	"math"
+
+	"github.com/anthonynsimon/bild/adjust"
+	"github.com/anthonynsimon/bild/transform"
+)
+
+// Resample filters.
+const (
+	// NearestNeighbor is the fastest resampling filter, no antialiasing.
+	NearestNeighbor int = iota
+	// Box filter (averaging pixels).
+	Box
+	// Linear is the bilinear filter, smooth and reasonably fast.
+	Linear
+	// MitchellNetravali is a smooth bicubic filter.
+	MitchellNetravali
+	// CatmullRom is a sharp bicubic filter.
+	CatmullRom
+	// Gaussian is a blurring filter that uses gaussian function, useful for noise removal.
+	Gaussian
+	// Lanczos is a high-quality resampling filter, it's slower than cubic filters.
+	Lanczos
+)
+
+var filters = map[int]transform.ResampleFilter{
+	NearestNeighbor:   transform.NearestNeighbor,
+	Box:               transform.Box,
+	Linear:            transform.Linear,
+	MitchellNetravali: transform.MitchellNetravali,
+	CatmullRom:        transform.CatmullRom,
+	Gaussian:          transform.Gaussian,
+	Lanczos:           transform.Lanczos,
+}
+
+func resize(img image.Image, width, height int, filter transform.ResampleFilter) *image.RGBA {
+	dstW, dstH := width, height
+
+	srcW := img.Bounds().Dx()
+	srcH := img.Bounds().Dy()
+
+	if dstW == 0 {
+		tmpW := float64(dstH) * float64(srcW) / float64(srcH)
+		dstW = int(math.Max(1.0, math.Floor(tmpW+0.5)))
+	}
+	if dstH == 0 {
+		tmpH := float64(dstW) * float64(srcH) / float64(srcW)
+		dstH = int(math.Max(1.0, math.Floor(tmpH+0.5)))
+	}
+
+	if srcW == dstW && srcH == dstH {
+		return imageToRGBA(img)
+	}
+
+	return transform.Resize(img, dstW, dstH, filter)
+}
+
+func fit(img image.Image, width, height int, filter transform.ResampleFilter) *image.RGBA {
+	maxW, maxH := width, height
+
+	b := img.Bounds()
+	srcW := b.Dx()
+	srcH := b.Dy()
+
+	if srcW <= maxW && srcH <= maxH {
+		return imageToRGBA(img)
+	}
+
+	srcAspectRatio := float64(srcW) / float64(srcH)
+	maxAspectRatio := float64(maxW) / float64(maxH)
+
+	var dstW, dstH int
+	if srcAspectRatio > maxAspectRatio {
+		dstW = maxW
+		dstH = int(float64(dstW) / srcAspectRatio)
+	} else {
+		dstH = maxH
+		dstW = int(float64(dstH) * srcAspectRatio)
+	}
+
+	return resize(img, dstW, dstH, filter)
+}
+
+func rotate(img image.Image, angle float64) *image.RGBA {
+	return transform.Rotate(img, angle, &transform.RotationOptions{ResizeBounds: true, Pivot: &image.Point{}})
+}
+
+func brightness(img image.Image, change float64) *image.RGBA {
+	return adjust.Brightness(img, change/100)
+}
+
+func contrast(img image.Image, change float64) *image.RGBA {
+	return adjust.Contrast(img, change/100)
+}
+
+// imageToRGBA converts an image.Image to *image.RGBA.
+func imageToRGBA(src image.Image) *image.RGBA {
+	if dst, ok := src.(*image.RGBA); ok {
+		return dst
+	}
+
+	b := src.Bounds()
+	dst := image.NewRGBA(b)
+	draw.Draw(dst, dst.Bounds(), src, b.Min, draw.Src)
+
+	return dst
+}
+
+// imageToGray converts an image.Image to *image.Gray.
+func imageToGray(src image.Image) *image.Gray {
+	if dst, ok := src.(*image.Gray); ok {
+		return dst
+	}
+
+	b := src.Bounds()
+	dst := image.NewGray(b)
+	draw.Draw(dst, dst.Bounds(), src, b.Min, draw.Src)
+
+	return dst
+}
+
+// isGrayScale checks if image is grayscale.
+func isGrayScale(img image.Image) bool {
+	model := img.ColorModel()
+	if model == color.GrayModel || model == color.Gray16Model {
+		return true
+	}
+
+	return false
+}