Add image.ReplacePixels; Add example/noise (#89)

example/noise/main.go

@@ -0,0 +1,69 @@
+// 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 main
+
+import (
+	"fmt"
+	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/ebitenutil"
+	"image"
+	"log"
+	//"math/rand"
+)
+
+const (
+	screenWidth  = 320
+	screenHeight = 240
+)
+
+var (
+	noiseImage *image.RGBA
+)
+
+type rand struct {
+	x, y, z, w uint32
+}
+
+func (r *rand) next() uint32 {
+	// math/rand is too slow to keep 60 FPS on web browsers.
+	// Use Xorshift instead: http://en.wikipedia.org/wiki/Xorshift
+	t := r.x ^ (r.x << 11)
+	r.x, r.y, r.z = r.y, r.z, r.w
+	r.w = (r.w ^ (r.w >> 19)) ^ (t ^ (t >> 8))
+	return r.w
+}
+
+var randInstance = &rand{12345678, 4185243, 776511, 45411}
+
+func update(screen *ebiten.Image) error {
+	const l = screenWidth * screenHeight
+	for i := 0; i < l; i++ {
+		x := randInstance.next()
+		noiseImage.Pix[4*i] = uint8(x >> 24)
+		noiseImage.Pix[4*i+1] = uint8(x >> 16)
+		noiseImage.Pix[4*i+2] = uint8(x >> 8)
+		noiseImage.Pix[4*i+3] = 0xff
+	}
+	screen.ReplacePixels(noiseImage.Pix)
+	ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %f", ebiten.CurrentFPS()))
+	return nil
+}
+
+func main() {
+	noiseImage = image.NewRGBA(image.Rect(0, 0, screenWidth, screenHeight))
+	if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Noise (Ebiten Demo)"); err != nil {
+		log.Fatal(err)
+	}
+}

gamecontext.go

@@ -69,6 +69,11 @@ func IsGamepadButtonPressed(id int, button GamepadButton) bool {
 }
 
 // NewImage returns an empty image.
+//
+// NewImage generates a new texture and a new framebuffer.
+// Be careful that image objects will never be released
+// even though nothing refers the image object and GC works.
+// It is because there is no way to define finalizers for Go objects if you use GopherJS.
 func NewImage(width, height int, filter Filter) (*Image, error) {
 	var img *Image
 	var err error

image.go

@@ -16,6 +16,7 @@ package ebiten
 
 import (
 	"errors"
+	"fmt"
 	"github.com/hajimehoshi/ebiten/internal"
 	"github.com/hajimehoshi/ebiten/internal/graphics"
 	"github.com/hajimehoshi/ebiten/internal/opengl"
@@ -162,6 +163,26 @@ func (i *Image) At(x, y int) color.Color {
 	return color.RGBA{r, g, b, a}
 }
 
+// ReplacePixels replaces the pixels of image with p.
+//
+// The given p must represent RGBA pre-multiplied alpha values.
+//
+// len(p) must equal to 4 * (image width) * (image height)
+//
+// This function may be slow.
+func (i *Image) ReplacePixels(p []uint8) error {
+	w, h := i.Size()
+	l := 4 * w * h
+	if len(p) != l {
+		return errors.New(fmt.Sprintf("p's length must be %d", l))
+	}
+	var err error
+	ui.Use(func(c *opengl.Context) {
+		err = i.texture.ReplacePixels(c, p)
+	})
+	return err
+}
+
 // A DrawImageOptions represents options to render an image on an image.
 type DrawImageOptions struct {
 	ImageParts ImageParts

internal/graphics/texture.go

@@ -90,3 +90,9 @@ func NewTextureFromImage(c *opengl.Context, img image.Image, filter opengl.Filte
 func (t *Texture) Dispose(c *opengl.Context) {
 	c.DeleteTexture(t.native)
 }
+
+func (t *Texture) ReplacePixels(c *opengl.Context, p []uint8) error {
+	c.BindTexture(t.native)
+	c.TexSubImage2D(p, t.width, t.height)
+	return nil
+}

internal/opengl/context.go

@@ -105,6 +105,10 @@ func (c *Context) DeleteTexture(t Texture) {
 	gl.Texture(t).Delete()
 }
 
+func (c *Context) TexSubImage2D(p []uint8, width, height int) {
+	gl.TexSubImage2D(gl.TEXTURE_2D, 0, 0, 0, width, height, gl.RGBA, gl.UNSIGNED_BYTE, p)
+}
+
 func (c *Context) NewFramebuffer(texture Texture) (Framebuffer, error) {
 	f := gl.GenFramebuffer()
 	f.Bind()

internal/opengl/context_js.go

@@ -103,6 +103,8 @@ func (c *Context) NewTexture(width, height int, pixels []uint8, filter Filter) (
 	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, int(filter))
 	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, int(filter))
 
+	// TODO: Can we use glTexSubImage2D with linear filtering?
+
 	// void texImage2D(GLenum target, GLint level, GLenum internalformat,
 	//     GLsizei width, GLsizei height, GLint border, GLenum format,
 	//     GLenum type, ArrayBufferView? pixels);
@@ -140,13 +142,12 @@ func (c *Context) DeleteTexture(t Texture) {
 	gl.DeleteTexture(t.Object)
 }
 
-func (c *Context) GlslHighpSupported() bool {
+func (c *Context) TexSubImage2D(p []uint8, width, height int) {
 	gl := c.gl
-	// headless-gl library may not define getShaderPrecisionFormat.
-	if gl.Get("getShaderPrecisionFormat") == js.Undefined {
-		return false
-	}
-	return gl.Call("getShaderPrecisionFormat", gl.FRAGMENT_SHADER, gl.HIGH_FLOAT).Get("precision").Int() != 0
+	// void texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
+	//                    GLsizei width, GLsizei height,
+	//                    GLenum format, GLenum type, ArrayBufferView? pixels);
+	gl.Call("texSubImage2D", gl.TEXTURE_2D, 0, 0, 0, width, height, gl.RGBA, gl.UNSIGNED_BYTE, p)
 }
 
 func (c *Context) NewFramebuffer(t Texture) (Framebuffer, error) {
@@ -216,6 +217,15 @@ func (c *Context) DeleteShader(s Shader) {
 	gl.DeleteShader(s.Object)
 }
 
+func (c *Context) GlslHighpSupported() bool {
+	gl := c.gl
+	// headless-gl library may not define getShaderPrecisionFormat.
+	if gl.Get("getShaderPrecisionFormat") == js.Undefined {
+		return false
+	}
+	return gl.Call("getShaderPrecisionFormat", gl.FRAGMENT_SHADER, gl.HIGH_FLOAT).Get("precision").Int() != 0
+}
+
 var lastProgramID ProgramID = 0
 
 func (c *Context) NewProgram(shaders []Shader) (Program, error) {