ebiten/internal/opengl/texture.go

// Copyright 2014 Hajime Hoshi
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package opengl

import (
	"errors"
	"fmt"
	"github.com/go-gl/gl"
	"github.com/hajimehoshi/ebiten/internal"
	"image"
	"image/draw"
)

func adjustImageForTexture(img image.Image) *image.RGBA {
	width, height := img.Bounds().Size().X, img.Bounds().Size().Y
	adjustedImageBounds := image.Rectangle{
		image.ZP,
		image.Point{
			internal.NextPowerOf2Int(width),
			internal.NextPowerOf2Int(height),
		},
	}
	if nrgba, ok := img.(*image.RGBA); ok && img.Bounds() == adjustedImageBounds {
		return nrgba
	}

	adjustedImage := image.NewRGBA(adjustedImageBounds)
	dstBounds := image.Rectangle{
		image.ZP,
		img.Bounds().Size(),
	}
	draw.Draw(adjustedImage, dstBounds, img, image.ZP, draw.Src)
	return adjustedImage
}

type Texture struct {
	native gl.Texture
	width  int
	height int
}

func (t *Texture) Native() gl.Texture {
	return t.native
}

func (t *Texture) Size() (width, height int) {
	return t.width, t.height
}

func createNativeTexture(textureWidth, textureHeight int, pixels []uint8, filter Filter) gl.Texture {
	nativeTexture := gl.GenTexture()
	if nativeTexture < 0 {
		panic("glGenTexture failed")
	}
	gl.PixelStorei(gl.UNPACK_ALIGNMENT, 4)
	nativeTexture.Bind(gl.TEXTURE_2D)
	defer gl.Texture(0).Bind(gl.TEXTURE_2D)

	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, int(filter))
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, int(filter))

	gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, textureWidth, textureHeight, 0, gl.RGBA, gl.UNSIGNED_BYTE, pixels)

	return nativeTexture
}

func NewTexture(width, height int, filter Filter) (*Texture, error) {
	w := internal.NextPowerOf2Int(width)
	h := internal.NextPowerOf2Int(height)
	if w < 4 {
		return nil, errors.New("width must be equal or more than 4.")
	}
	if h < 4 {
		return nil, errors.New("height must be equal or more than 4.")
	}
	native := createNativeTexture(w, h, nil, filter)
	return &Texture{native, width, height}, nil
}

func NewTextureFromImage(img image.Image, filter Filter) (*Texture, error) {
	origSize := img.Bounds().Size()
	if origSize.X < 4 {
		return nil, errors.New("width must be equal or more than 4.")
	}
	if origSize.Y < 4 {
		return nil, errors.New("height must be equal or more than 4.")
	}
	adjustedImage := adjustImageForTexture(img)
	size := adjustedImage.Bounds().Size()
	native := createNativeTexture(size.X, size.Y, adjustedImage.Pix, filter)
	return &Texture{native, origSize.X, origSize.Y}, nil
}

func (t *Texture) Dispose() {
	t.native.Delete()
}

func (t *Texture) Pixels() ([]uint8, error) {
	w, h := internal.NextPowerOf2Int(t.width), internal.NextPowerOf2Int(t.height)
	pixels := make([]uint8, 4*w*h)
	t.native.Bind(gl.TEXTURE_2D)
	gl.GetTexImage(gl.TEXTURE_2D, 0, gl.RGBA, gl.UNSIGNED_BYTE, pixels)
	if e := gl.GetError(); e != gl.NO_ERROR {
		// TODO: Use glu.ErrorString
		return nil, errors.New(fmt.Sprintf("gl error: %d", e))
	}
	return pixels, nil
}