Introduce Photoshop-like alpha blending

example/blocks/blocks/font.go

@@ -32,7 +32,7 @@ func textWidth(str string) int {
 	return charWidth * len(str)
 }
 
-func drawText(context ebiten.GraphicsContext, textures *Textures, str string, x, y, scale int, clr color.Color) {
+func drawText(context ebiten.GraphicsContext, textures *Textures, str string, ox, oy, scale int, clr color.Color) {
 	fontTextureId := textures.GetTexture("font")
 	parts := []ebiten.TexturePart{}
 
@@ -53,11 +53,9 @@ func drawText(context ebiten.GraphicsContext, textures *Textures, str string, x,
 		locationX += charWidth
 	}
 
-	geoMat := ebiten.GeometryMatrixI()
+	geoMat := ebiten.ScaleGeometry(float64(scale), float64(scale))
-	geoMat.Concat(ebiten.ScaleGeometry(float64(scale), float64(scale)))
+	geoMat.Concat(ebiten.TranslateGeometry(float64(ox), float64(oy)))
-	geoMat.Concat(ebiten.TranslateGeometry(float64(x), float64(y)))
+	clrMat := ebiten.ScaleColor(clr)
-	clrMat := ebiten.ColorMatrixI()
-	clrMat.Concat(ebiten.ScaleColor(clr))
 	context.DrawTexture(fontTextureId, parts, geoMat, clrMat)
 }
 

graphics.go

@@ -17,6 +17,7 @@ limitations under the License.
 package ebiten
 
 import (
+	"github.com/hajimehoshi/ebiten/internal"
 	"github.com/hajimehoshi/ebiten/internal/opengl"
 	"github.com/hajimehoshi/ebiten/internal/opengl/internal/shader"
 )
@@ -92,11 +93,11 @@ func (r *RenderTarget) Size() (width int, height int) {
 }
 
 func u(x float64, width int) float32 {
-	return float32(x) / float32(opengl.AdjustSizeForTexture(width))
+	return float32(x) / float32(internal.AdjustSizeForTexture(width))
 }
 
 func v(y float64, height int) float32 {
-	return float32(y) / float32(opengl.AdjustSizeForTexture(height))
+	return float32(y) / float32(internal.AdjustSizeForTexture(height))
 }
 
 func textureQuads(parts []TexturePart, width, height int) []shader.TextureQuad {

graphicscontext.go

@@ -22,8 +22,10 @@ import (
 )
 
 func newGraphicsContext(screenWidth, screenHeight, screenScale int) (*graphicsContext, error) {
-	// The defualt framebuffer should be 0.
+	r, t, err := opengl.NewZeroRenderTarget(screenWidth*screenScale, screenHeight*screenScale, true)
-	r := opengl.NewRenderTarget(screenWidth*screenScale, screenHeight*screenScale, true)
+	if err != nil {
+		return nil, err
+	}
 
 	screen, err := idsInstance.createRenderTarget(screenWidth, screenHeight, gl.NEAREST)
 	if err != nil {
@@ -32,7 +34,7 @@ func newGraphicsContext(screenWidth, screenHeight, screenScale int) (*graphicsCo
 
 	c := &graphicsContext{
 		currents:     make([]*RenderTarget, 1),
-		defaultR:     &RenderTarget{r, nil},
+		defaultR:     &RenderTarget{r, &Texture{t}},
 		screen:       screen,
 		screenWidth:  screenWidth,
 		screenHeight: screenHeight,

ids.go

@@ -67,7 +67,9 @@ func (i *ids) drawTexture(target *RenderTarget, texture *Texture, parts []Textur
 	}
 	projectionMatrix := target.glRenderTarget.ProjectionMatrix()
 	quads := textureQuads(parts, glTexture.Width(), glTexture.Height())
-	shader.DrawTexture(glTexture.Native(), projectionMatrix, quads, &geo, &color)
+	w, h := target.Size()
+	shader.DrawTexture(glTexture.Native(), target.texture.glTexture.Native(), w, h, projectionMatrix, quads, &geo, &color)
+	gl.Flush()
 	return nil
 }
 

internal/math.go

@@ -0,0 +1,32 @@
+/*
+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 internal
+
+func NextPowerOf2(x uint64) uint64 {
+	x -= 1
+	x |= (x >> 1)
+	x |= (x >> 2)
+	x |= (x >> 4)
+	x |= (x >> 8)
+	x |= (x >> 16)
+	x |= (x >> 32)
+	return x + 1
+}
+
+func AdjustSizeForTexture(size int) int {
+	return int(NextPowerOf2(uint64(size)))
+}

internal/math_test.go

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package opengl_test
+package internal_test
 
 import (
 	. "."
@@ -35,8 +35,7 @@ func TestNextPowerOf2(t *testing.T) {
 		got := NextPowerOf2(testCase.arg)
 		wanted := testCase.expected
 		if wanted != got {
-			t.Errorf("Clp(%d) = %d, wanted %d",
+			t.Errorf("Clp(%d) = %d, wanted %d", testCase.arg, got, wanted)
-				testCase.arg, got, wanted)
 		}
 
 	}

internal/opengl/internal/shader/drawtexture.go

@@ -18,6 +18,7 @@ package shader
 
 import (
 	"github.com/go-gl/gl"
+	"github.com/hajimehoshi/ebiten/internal"
 	"sync"
 )
 
@@ -38,7 +39,7 @@ type Matrix interface {
 }
 
 // TODO: Use VBO
-func DrawTexture(native gl.Texture, projectionMatrix [4][4]float64, quads []TextureQuad, geo Matrix, color Matrix) {
+func DrawTexture(native gl.Texture, target gl.Texture, width, height int, projectionMatrix [4][4]float64, quads []TextureQuad, geo Matrix, color Matrix) {
 	once.Do(func() {
 		initialize()
 	})
@@ -47,27 +48,39 @@ func DrawTexture(native gl.Texture, projectionMatrix [4][4]float64, quads []Text
 		return
 	}
 	// TODO: Check performance
-	shaderProgram := use(glMatrix(projectionMatrix), geo, color)
+	shaderProgram := use(glMatrix(projectionMatrix), width, height, geo, color)
 
+	gl.ActiveTexture(gl.TEXTURE0)
 	native.Bind(gl.TEXTURE_2D)
-	defer gl.Texture(0).Bind(gl.TEXTURE_2D)
+
+	gl.ActiveTexture(gl.TEXTURE1)
+	target.Bind(gl.TEXTURE_2D)
+
+	texture0UniformLocation := getUniformLocation(shaderProgram, "texture0")
+	texture1UniformLocation := getUniformLocation(shaderProgram, "texture1")
+	texture0UniformLocation.Uniform1i(0)
+	texture1UniformLocation.Uniform1i(1)
 
 	vertexAttrLocation := getAttributeLocation(shaderProgram, "vertex")
-	texCoordAttrLocation := getAttributeLocation(shaderProgram, "tex_coord")
+	texCoord0AttrLocation := getAttributeLocation(shaderProgram, "tex_coord0")
+	texCoord1AttrLocation := getAttributeLocation(shaderProgram, "tex_coord1")
 
 	gl.EnableClientState(gl.VERTEX_ARRAY)
 	gl.EnableClientState(gl.TEXTURE_COORD_ARRAY)
 	vertexAttrLocation.EnableArray()
-	texCoordAttrLocation.EnableArray()
+	texCoord0AttrLocation.EnableArray()
+	texCoord1AttrLocation.EnableArray()
 	defer func() {
-		texCoordAttrLocation.DisableArray()
+		texCoord1AttrLocation.DisableArray()
+		texCoord0AttrLocation.DisableArray()
 		vertexAttrLocation.DisableArray()
 		gl.DisableClientState(gl.TEXTURE_COORD_ARRAY)
 		gl.DisableClientState(gl.VERTEX_ARRAY)
 	}()
 
 	vertices := []float32{}
-	texCoords := []float32{}
+	texCoords0 := []float32{}
+	texCoords1 := []float32{}
 	indicies := []uint32{}
 	// TODO: Check len(quads) and gl.MAX_ELEMENTS_INDICES?
 	for i, quad := range quads {
@@ -85,12 +98,24 @@ func DrawTexture(native gl.Texture, projectionMatrix [4][4]float64, quads []Text
 		u2 := quad.TextureCoordU2
 		v1 := quad.TextureCoordV1
 		v2 := quad.TextureCoordV2
-		texCoords = append(texCoords,
+		texCoords0 = append(texCoords0,
 			u1, v1,
 			u2, v1,
 			u1, v2,
 			u2, v2,
 		)
+		w := float32(internal.AdjustSizeForTexture(width))
+		h := float32(internal.AdjustSizeForTexture(height))
+		xx1 := x1 / w
+		xx2 := x2 / w
+		yy1 := y1 / h
+		yy2 := y2 / h
+		texCoords1 = append(texCoords1,
+			xx1, yy1,
+			xx2, yy1,
+			xx1, yy2,
+			xx2, yy2,
+		)
 		base := uint32(i * 4)
 		indicies = append(indicies,
 			base, base+1, base+2,
@@ -98,6 +123,7 @@ func DrawTexture(native gl.Texture, projectionMatrix [4][4]float64, quads []Text
 		)
 	}
 	vertexAttrLocation.AttribPointer(2, gl.FLOAT, false, 0, vertices)
-	texCoordAttrLocation.AttribPointer(2, gl.FLOAT, false, 0, texCoords)
+	texCoord0AttrLocation.AttribPointer(2, gl.FLOAT, false, 0, texCoords0)
+	texCoord1AttrLocation.AttribPointer(2, gl.FLOAT, false, 0, texCoords1)
 	gl.DrawElements(gl.TRIANGLES, len(indicies), gl.UNSIGNED_INT, indicies)
 }

internal/opengl/internal/shader/program.go

@@ -18,6 +18,7 @@ package shader
 
 import (
 	"github.com/go-gl/gl"
+	"github.com/hajimehoshi/ebiten/internal"
 )
 
 type program struct {
@@ -80,7 +81,7 @@ func getUniformLocation(program gl.Program, name string) gl.UniformLocation {
 	return location
 }
 
-func use(projectionMatrix [16]float32, geo Matrix, color Matrix) gl.Program {
+func use(projectionMatrix [16]float32, width, height int, geo Matrix, color Matrix) gl.Program {
 	// TODO: Check the performance.
 	program := programColorMatrix
 
@@ -99,6 +100,15 @@ func use(projectionMatrix [16]float32, geo Matrix, color Matrix) gl.Program {
 		tx, ty, 0, 1,
 	}
 	getUniformLocation(program.native, "modelview_matrix").UniformMatrix4fv(false, glModelviewMatrix)
+	txn := tx / float32(internal.AdjustSizeForTexture(width))
+	tyn := ty / float32(internal.AdjustSizeForTexture(height))
+	glModelviewMatrixN := [...]float32{
+		a, c, 0, 0,
+		b, d, 0, 0,
+		0, 0, 1, 0,
+		txn, tyn, 0, 1,
+	}
+	getUniformLocation(program.native, "modelview_matrix_n").UniformMatrix4fv(false, glModelviewMatrixN)
 
 	getUniformLocation(program.native, "texture").Uniform1i(0)
 

internal/opengl/internal/shader/shader.go

@@ -42,41 +42,53 @@ var shaders = map[shaderId]*shader{
 		source: `
 uniform mat4 projection_matrix;
 uniform mat4 modelview_matrix;
+uniform mat4 modelview_matrix_n;
 attribute vec2 vertex;
-attribute vec2 tex_coord;
+attribute vec2 tex_coord0;
-varying vec2 vertex_out_tex_coord;
+attribute vec2 tex_coord1;
+varying vec2 vertex_out_tex_coord0;
+varying vec2 vertex_out_tex_coord1;
 
 void main(void) {
-  vertex_out_tex_coord = tex_coord;
+  vertex_out_tex_coord0 = tex_coord0;
+  vertex_out_tex_coord1 = (modelview_matrix_n * vec4(tex_coord1, 0, 1)).xy;
   gl_Position = projection_matrix * modelview_matrix * vec4(vertex, 0, 1);
 }
 `,
 	},
+	// TODO: Now this shader is not used
 	shaderFragment: {
 		shaderType: gl.FRAGMENT_SHADER,
 		source: `
 uniform sampler2D texture;
-varying vec2 vertex_out_tex_coord;
+varying vec2 vertex_out_tex_coord0;
 
 void main(void) {
-  gl_FragColor = texture2D(texture, vertex_out_tex_coord);
+  gl_FragColor = texture2D(texture, vertex_out_tex_coord0);
 }
 `,
 	},
 	shaderColorMatrix: {
 		shaderType: gl.FRAGMENT_SHADER,
 		source: `
-uniform sampler2D texture;
+uniform sampler2D texture0;
+uniform sampler2D texture1;
 uniform mat4 color_matrix;
 uniform vec4 color_matrix_translation;
-varying vec2 vertex_out_tex_coord;
+varying vec2 vertex_out_tex_coord0;
+varying vec2 vertex_out_tex_coord1;
 
 void main(void) {
-  vec4 color = texture2D(texture, vertex_out_tex_coord);
+  vec4 color0 = texture2D(texture0, vertex_out_tex_coord0);
-  gl_FragColor = (color_matrix * color) + color_matrix_translation;
+  vec4 color1 = texture2D(texture1, vertex_out_tex_coord1);
+  color0 = (color_matrix * color0) + color_matrix_translation;
+
+  gl_FragColor.a = color0.a + color1.a - color0.a * color1.a;
+  gl_FragColor.rgb = (color0.a * color0.rgb + (1.0 - color0.a) * color1.a * color1.rgb) / gl_FragColor.a;
 }
 `,
 	},
+	// TODO: Now this shader is not used
 	shaderSolidColor: {
 		shaderType: gl.FRAGMENT_SHADER,
 		source: `

internal/opengl/internal/shader/texturequad.go

@@ -16,6 +16,7 @@ limitations under the License.
 
 package shader
 
+// TODO: Rename X1, X2 -> X0, X1
 type TextureQuad struct {
 	VertexX1       float32
 	VertexX2       float32

internal/opengl/rendertarget.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"fmt"
 	"github.com/go-gl/gl"
+	"github.com/hajimehoshi/ebiten/internal"
 )
 
 func orthoProjectionMatrix(left, right, bottom, top int) [4][4]float64 {
@@ -43,12 +44,23 @@ type RenderTarget struct {
 	flipY       bool
 }
 
-func NewRenderTarget(width, height int, flipY bool) *RenderTarget {
+func NewZeroRenderTarget(width, height int, flipY bool) (*RenderTarget, *Texture, error) {
-	return &RenderTarget{
+	r := &RenderTarget{
 		width:  width,
 		height: height,
 		flipY:  flipY,
 	}
+	// The framebuffer 0 can't be enlarged, so any filter is acceptable.
+	t, err := NewTexture(width, height, gl.NEAREST)
+	if err != nil {
+		return nil, nil, err
+	}
+	// TODO: Does this affect the current rendering target?
+	gl.Framebuffer(0).Bind()
+	if err := framebufferTexture(t.native); err != nil {
+		return nil, nil, err
+	}
+	return r, t, err
 }
 
 func NewRenderTargetFromTexture(texture *Texture) (*RenderTarget, error) {
@@ -80,22 +92,28 @@ func (r *RenderTarget) Dispose() {
 }
 
 func createFramebuffer(nativeTexture gl.Texture) (gl.Framebuffer, error) {
+	// TODO: Does this affect the current rendering target?
 	framebuffer := gl.GenFramebuffer()
 	framebuffer.Bind()
 
-	gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, nativeTexture, 0)
+	if err := framebufferTexture(nativeTexture); err != nil {
-	if gl.CheckFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE {
+		return 0, err
-		return 0, errors.New("creating framebuffer failed")
 	}
 
-	// Set this framebuffer opaque because alpha values on a target might be
-	// confusing.
-	gl.ClearColor(0, 0, 0, 1)
-	gl.Clear(gl.COLOR_BUFFER_BIT)
-
 	return framebuffer, nil
 }
 
+func framebufferTexture(nativeTexture gl.Texture) error {
+	gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, nativeTexture, 0)
+	if gl.CheckFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE {
+		return errors.New("creating framebuffer failed")
+	}
+
+	gl.ClearColor(0, 0, 0, 0)
+	gl.Clear(gl.COLOR_BUFFER_BIT)
+	return nil
+}
+
 func (r *RenderTarget) SetAsViewport() error {
 	gl.Flush()
 	r.framebuffer.Bind()
@@ -104,21 +122,19 @@ func (r *RenderTarget) SetAsViewport() error {
 		return errors.New(fmt.Sprintf("glBindFramebuffer failed: %d", err))
 	}
 
-	gl.BlendFuncSeparate(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA, gl.ZERO, gl.ONE)
+	width := internal.AdjustSizeForTexture(r.width)
-
+	height := internal.AdjustSizeForTexture(r.height)
-	width := AdjustSizeForTexture(r.width)
-	height := AdjustSizeForTexture(r.height)
 	gl.Viewport(0, 0, width, height)
 	return nil
 }
 
 func (r *RenderTarget) ProjectionMatrix() [4][4]float64 {
-	width := AdjustSizeForTexture(r.width)
+	width := internal.AdjustSizeForTexture(r.width)
-	height := AdjustSizeForTexture(r.height)
+	height := internal.AdjustSizeForTexture(r.height)
 	m := orthoProjectionMatrix(0, width, 0, height)
 	if r.flipY {
 		m[1][1] *= -1
-		m[1][3] += float64(r.height) / float64(AdjustSizeForTexture(r.height)) * 2
+		m[1][3] += float64(r.height) / float64(internal.AdjustSizeForTexture(r.height)) * 2
 	}
 	return m
 }

internal/opengl/texture.go

@@ -18,32 +18,18 @@ package opengl
 
 import (
 	"github.com/go-gl/gl"
+	"github.com/hajimehoshi/ebiten/internal"
 	"image"
 	"image/draw"
 )
 
-func NextPowerOf2(x uint64) uint64 {
-	x -= 1
-	x |= (x >> 1)
-	x |= (x >> 2)
-	x |= (x >> 4)
-	x |= (x >> 8)
-	x |= (x >> 16)
-	x |= (x >> 32)
-	return x + 1
-}
-
-func AdjustSizeForTexture(size int) int {
-	return int(NextPowerOf2(uint64(size)))
-}
-
 func adjustImageForTexture(img image.Image) *image.NRGBA {
 	width, height := img.Bounds().Size().X, img.Bounds().Size().Y
 	adjustedImageBounds := image.Rectangle{
 		image.ZP,
 		image.Point{
-			AdjustSizeForTexture(width),
+			internal.AdjustSizeForTexture(width),
-			AdjustSizeForTexture(height),
+			internal.AdjustSizeForTexture(height),
 		},
 	}
 	if nrgba, ok := img.(*image.NRGBA); ok && img.Bounds() == adjustedImageBounds {
@@ -95,8 +81,8 @@ func createNativeTexture(textureWidth, textureHeight int, pixels []uint8, filter
 }
 
 func NewTexture(width, height int, filter int) (*Texture, error) {
-	w := AdjustSizeForTexture(width)
+	w := internal.AdjustSizeForTexture(width)
-	h := AdjustSizeForTexture(height)
+	h := internal.AdjustSizeForTexture(height)
 	native := createNativeTexture(w, h, nil, filter)
 	return &Texture{native, width, height}, nil
 }

ui.go

@@ -52,7 +52,6 @@ func init() {
 	currentUI.use(func() {
 		gl.Init()
 		gl.Enable(gl.TEXTURE_2D)
-		gl.Enable(gl.BLEND)
 	})
 }