gfx.go

package main

import (
	"errors"
	"image"
	"image/draw"
	_ "image/png"
	"os"

	"github.com/go-gl/gl/all-core/gl"
)

// loadImage opens an image file, upload it the the GPU and returns the texture id
func loadImage(file string) (uint32, error) {
	imgFile, err := os.Open(file)
	if err != nil {
		return 0, err
	}
	img, _, err := image.Decode(imgFile)
	if err != nil {
		return 0, err
	}

	rgba := image.NewRGBA(img.Bounds())
	if rgba.Stride != rgba.Rect.Size().X*4 {
		return 0, errors.New("incorrect stride")
	}
	draw.Draw(rgba, rgba.Bounds(), img, image.Point{0, 0}, draw.Src)

	return loadTexture(rgba), nil
}

func loadTexture(rgba *image.RGBA) uint32 {
	var texture uint32
	gl.GenTextures(1, &texture)
	gl.ActiveTexture(gl.TEXTURE1)
	gl.BindTexture(gl.TEXTURE_2D, texture)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
	gl.PixelStorei(gl.UNPACK_ROW_LENGTH, 0)
	gl.TexImage2D(
		gl.TEXTURE_2D,
		0,
		gl.RGBA,
		int32(rgba.Rect.Size().X),
		int32(rgba.Rect.Size().Y),
		0,
		gl.RGBA,
		gl.UNSIGNED_BYTE,
		gl.Ptr(rgba.Pix))

	return texture
}