canvas/images.go

package canvas

import (
	"bytes"
	"errors"
	"image"
	"io/ioutil"
)

type Image struct {
	w, h int
	tex  uint32
}

func LoadImage(src interface{}) (*Image, error) {
	switch v := src.(type) {
	case *image.RGBA:
		return loadImageRGBA(v)
	case *image.Gray:
		return loadImageGray(v)
	case image.Image:
		return loadImageConverted(v)
	case string:
		data, err := ioutil.ReadFile(v)
		if err != nil {
			return nil, err
		}
		img, _, err := image.Decode(bytes.NewReader(data))
		if err != nil {
			return nil, err
		}
		return LoadImage(img)
	case []byte:
		img, _, err := image.Decode(bytes.NewReader(v))
		if err != nil {
			return nil, err
		}
		return LoadImage(img)
	}
	return nil, errors.New("Unsupported source type")
}

func loadImageRGBA(src *image.RGBA) (*Image, error) {
	img := &Image{w: src.Bounds().Dx(), h: src.Bounds().Dy()}
	gli.GenTextures(1, &img.tex)
	gli.BindTexture(gl_TEXTURE_2D, img.tex)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_MIN_FILTER, gl_LINEAR_MIPMAP_LINEAR)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_MAG_FILTER, gl_LINEAR)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_WRAP_S, gl_CLAMP_TO_EDGE)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_WRAP_T, gl_CLAMP_TO_EDGE)
	if err := glError(); err != nil {
		return nil, err
	}
	if src.Stride == img.w*4 {
		gli.TexImage2D(gl_TEXTURE_2D, 0, gl_RGBA, int32(img.w), int32(img.h), 0, gl_RGBA, gl_UNSIGNED_BYTE, gli.Ptr(&src.Pix[0]))
	} else {
		data := make([]uint8, 0, img.w*img.h*4)
		for y := 0; y < img.h; y++ {
			start := y * src.Stride
			end := start + img.w*4
			data = append(data, src.Pix[start:end]...)
		}
		gli.TexImage2D(gl_TEXTURE_2D, 0, gl_RGBA, int32(img.w), int32(img.h), 0, gl_RGBA, gl_UNSIGNED_BYTE, gli.Ptr(&data[0]))
	}
	if err := glError(); err != nil {
		return nil, err
	}
	gli.GenerateMipmap(gl_TEXTURE_2D)
	if err := glError(); err != nil {
		return nil, err
	}
	return img, nil
}

func loadImageGray(src *image.Gray) (*Image, error) {
	img := &Image{w: src.Bounds().Dx(), h: src.Bounds().Dy()}
	gli.GenTextures(1, &img.tex)
	gli.BindTexture(gl_TEXTURE_2D, img.tex)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_MIN_FILTER, gl_LINEAR_MIPMAP_LINEAR)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_MAG_FILTER, gl_LINEAR)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_WRAP_S, gl_CLAMP_TO_EDGE)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_WRAP_T, gl_CLAMP_TO_EDGE)
	if err := glError(); err != nil {
		return nil, err
	}
	if src.Stride == img.w {
		gli.TexImage2D(gl_TEXTURE_2D, 0, gl_RED, int32(img.w), int32(img.h), 0, gl_RED, gl_UNSIGNED_BYTE, gli.Ptr(&src.Pix[0]))
	} else {
		data := make([]uint8, 0, img.w*img.h)
		for y := 0; y < img.h; y++ {
			start := y * src.Stride
			end := start + img.w
			data = append(data, src.Pix[start:end]...)
		}
		gli.TexImage2D(gl_TEXTURE_2D, 0, gl_RED, int32(img.w), int32(img.h), 0, gl_RED, gl_UNSIGNED_BYTE, gli.Ptr(&data[0]))
	}
	if err := glError(); err != nil {
		return nil, err
	}
	gli.GenerateMipmap(gl_TEXTURE_2D)
	if err := glError(); err != nil {
		return nil, err
	}
	return img, nil
}

func loadImageConverted(src image.Image) (*Image, error) {
	img := &Image{w: src.Bounds().Dx(), h: src.Bounds().Dy()}
	gli.GenTextures(1, &img.tex)
	gli.BindTexture(gl_TEXTURE_2D, img.tex)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_MIN_FILTER, gl_LINEAR_MIPMAP_LINEAR)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_MAG_FILTER, gl_LINEAR)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_WRAP_S, gl_CLAMP_TO_EDGE)
	gli.TexParameteri(gl_TEXTURE_2D, gl_TEXTURE_WRAP_T, gl_CLAMP_TO_EDGE)
	if err := glError(); err != nil {
		return nil, err
	}
	data := make([]uint8, 0, img.w*img.h*4)
	for y := 0; y < img.h; y++ {
		for x := 0; x < img.w; x++ {
			ir, ig, ib, ia := src.At(x, y).RGBA()
			r, g, b, a := uint8(ir>>8), uint8(ig>>8), uint8(ib>>8), uint8(ia>>8)
			data = append(data, r, g, b, a)
		}
	}
	gli.TexImage2D(gl_TEXTURE_2D, 0, gl_RGBA, int32(img.w), int32(img.h), 0, gl_RGBA, gl_UNSIGNED_BYTE, gli.Ptr(&data[0]))
	if err := glError(); err != nil {
		return nil, err
	}
	gli.GenerateMipmap(gl_TEXTURE_2D)
	if err := glError(); err != nil {
		return nil, err
	}
	return img, nil
}

func (img *Image) W() int           { return img.w }
func (img *Image) H() int           { return img.h }
func (img *Image) Size() (int, int) { return img.w, img.h }