graphics: Add 'screen' filter for fast rendering (#509)

graphics.go

@@ -31,6 +31,9 @@ const (
 
 	// FilterLinear represents linear filter
 	FilterLinear Filter = Filter(graphics.FilterLinear)
+
+	// filterScreen represents a special filter for screen. Inner usage only.
+	filterScreen Filter = Filter(graphics.FilterScreen)
 )
 
 // CompositeMode represents Porter-Duff composition mode.

graphicscontext.go

@@ -15,8 +15,6 @@
 package ebiten
 
 import (
-	"math"
-
 	"github.com/hajimehoshi/ebiten/internal/clock"
 	"github.com/hajimehoshi/ebiten/internal/hooks"
 	"github.com/hajimehoshi/ebiten/internal/restorable"
@@ -33,7 +31,6 @@ func newGraphicsContext(f func(*Image) error) *graphicsContext {
 type graphicsContext struct {
 	f           func(*Image) error
 	offscreen   *Image
-	offscreen2  *Image // TODO: better name
 	screen      *Image
 	initialized bool
 	invalidated bool // browser only
@@ -54,24 +51,15 @@ func (c *graphicsContext) SetSize(screenWidth, screenHeight int, screenScale flo
 	if c.offscreen != nil {
 		_ = c.offscreen.Dispose()
 	}
-	if c.offscreen2 != nil {
-		_ = c.offscreen2.Dispose()
-	}
 	offscreen := newVolatileImage(screenWidth, screenHeight, FilterDefault)
 
-	intScreenScale := int(math.Ceil(screenScale))
-	w := screenWidth * intScreenScale
-	h := screenHeight * intScreenScale
-	offscreen2 := newVolatileImage(w, h, FilterDefault)
-
-	w = int(float64(screenWidth) * screenScale)
-	h = int(float64(screenHeight) * screenScale)
+	w := int(float64(screenWidth) * screenScale)
+	h := int(float64(screenHeight) * screenScale)
 	ox, oy := ui.ScreenOffset()
 	c.screen = newImageWithScreenFramebuffer(w, h, ox, oy)
 	_ = c.screen.Clear()
 
 	c.offscreen = offscreen
-	c.offscreen2 = offscreen2
 }
 
 func (c *graphicsContext) initializeIfNeeded() error {
@@ -117,8 +105,7 @@ func (c *graphicsContext) Update(afterFrameUpdate func()) error {
 		afterFrameUpdate()
 	}
 	if 0 < updateCount {
-		drawWithFittingScale(c.offscreen2, c.offscreen, FilterNearest)
-		drawWithFittingScale(c.screen, c.offscreen2, FilterLinear)
+		drawWithFittingScale(c.screen, c.offscreen, filterScreen)
 	}
 
 	if err := restorable.ResolveStaleImages(); err != nil {

internal/graphics/command.go

@@ -247,12 +247,9 @@ func (c *drawImageCommand) Exec(indexOffsetInBytes int) error {
 	if n == 0 {
 		return nil
 	}
-	sw, sh := c.src.Size()
-	sw = emath.NextPowerOf2Int(sw)
-	sh = emath.NextPowerOf2Int(sh)
 	_, dh := c.dst.Size()
 	proj := f.projectionMatrix(dh)
-	theOpenGLState.useProgram(proj, c.src.texture.native, sw, sh, c.color, c.filter)
+	theOpenGLState.useProgram(proj, c.src.texture.native, c.dst, c.src, c.color, c.filter)
 	// TODO: We should call glBindBuffer here?
 	// The buffer is already bound at begin() but it is counterintuitive.
 	opengl.GetContext().DrawElements(opengl.Triangles, 6*n, indexOffsetInBytes)

internal/graphics/program.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 
 	"github.com/hajimehoshi/ebiten/internal/affine"
+	emath "github.com/hajimehoshi/ebiten/internal/math"
 	"github.com/hajimehoshi/ebiten/internal/opengl"
 )
 
@@ -110,6 +111,8 @@ type openGLState struct {
 	// programLinear is OpenGL's program for rendering a texture with linear filter.
 	programLinear opengl.Program
 
+	programScreen opengl.Program
+
 	lastProgram                opengl.Program
 	lastProjectionMatrix       []float32
 	lastColorMatrix            []float32
@@ -157,6 +160,9 @@ func (s *openGLState) reset() error {
 	if s.programLinear != zeroProgram {
 		opengl.GetContext().DeleteProgram(s.programLinear)
 	}
+	if s.programScreen != zeroProgram {
+		opengl.GetContext().DeleteProgram(s.programScreen)
+	}
 	if s.arrayBuffer != zeroBuffer {
 		opengl.GetContext().DeleteBuffer(s.arrayBuffer)
 	}
@@ -182,6 +188,12 @@ func (s *openGLState) reset() error {
 	}
 	defer opengl.GetContext().DeleteShader(shaderFragmentLinearNative)
 
+	shaderFragmentScreenNative, err := opengl.GetContext().NewShader(opengl.FragmentShader, shader(shaderFragmentScreen))
+	if err != nil {
+		panic(fmt.Sprintf("graphics: shader compiling error:\n%s", err))
+	}
+	defer opengl.GetContext().DeleteShader(shaderFragmentScreenNative)
+
 	s.programNearest, err = opengl.GetContext().NewProgram([]opengl.Shader{
 		shaderVertexModelviewNative,
 		shaderFragmentNearestNative,
@@ -198,6 +210,14 @@ func (s *openGLState) reset() error {
 		return err
 	}
 
+	s.programScreen, err = opengl.GetContext().NewProgram([]opengl.Shader{
+		shaderVertexModelviewNative,
+		shaderFragmentScreenNative,
+	})
+	if err != nil {
+		return err
+	}
+
 	s.arrayBuffer = theArrayBufferLayout.newArrayBuffer()
 
 	indices := make([]uint16, 6*maxQuads)
@@ -228,7 +248,7 @@ func areSameFloat32Array(a, b []float32) bool {
 }
 
 // useProgram uses the program (programTexture).
-func (s *openGLState) useProgram(proj []float32, texture opengl.Texture, sourceWidth, sourceHeight int, colorM affine.ColorM, filter Filter) {
+func (s *openGLState) useProgram(proj []float32, texture opengl.Texture, dst, src *Image, colorM affine.ColorM, filter Filter) {
 	c := opengl.GetContext()
 
 	var program opengl.Program
@@ -237,6 +257,8 @@ func (s *openGLState) useProgram(proj []float32, texture opengl.Texture, sourceW
 		program = s.programNearest
 	case FilterLinear:
 		program = s.programLinear
+	case FilterScreen:
+		program = s.programScreen
 	default:
 		panic("not reached")
 	}
@@ -287,14 +309,23 @@ func (s *openGLState) useProgram(proj []float32, texture opengl.Texture, sourceW
 		s.lastColorMatrixTranslation = esTranslate
 	}
 
-	if program == s.programLinear {
-		if s.lastSourceWidth != sourceWidth || s.lastSourceHeight != sourceHeight {
-			c.UniformFloats(program, "source_size",
-				[]float32{float32(sourceWidth), float32(sourceHeight)})
-			s.lastSourceWidth = sourceWidth
-			s.lastSourceHeight = sourceHeight
+	if program == s.programLinear || program == s.programScreen {
+		sw, sh := src.Size()
+		sw = emath.NextPowerOf2Int(sw)
+		sh = emath.NextPowerOf2Int(sh)
+
+		if s.lastSourceWidth != sw || s.lastSourceHeight != sh {
+			c.UniformFloats(program, "source_size", []float32{float32(sw), float32(sh)})
+			s.lastSourceWidth = sw
+			s.lastSourceHeight = sh
 		}
 	}
+	if program == s.programScreen {
+		sw, _ := src.Size()
+		dw, _ := dst.Size()
+		scale := float32(dw) / float32(sw)
+		c.UniformFloat(program, "scale", scale)
+	}
 
 	// We don't have to call gl.ActiveTexture here: GL_TEXTURE0 is the default active texture
 	// See also: https://www.opengl.org/sdk/docs/man2/xhtml/glActiveTexture.xml

internal/graphics/shader.go

@@ -24,6 +24,7 @@ const (
 	shaderVertexModelview shaderID = iota
 	shaderFragmentNearest
 	shaderFragmentLinear
+	shaderFragmentScreen
 )
 
 func shader(id shaderID) string {
@@ -36,6 +37,8 @@ func shader(id shaderID) string {
 		defs = append(defs, "#define FILTER_NEAREST")
 	case shaderFragmentLinear:
 		defs = append(defs, "#define FILTER_LINEAR")
+	case shaderFragmentScreen:
+		defs = append(defs, "#define FILTER_SCREEN")
 	default:
 		panic("not reached")
 	}
@@ -73,10 +76,14 @@ uniform sampler2D texture;
 uniform mat4 color_matrix;
 uniform vec4 color_matrix_translation;
 
-#if defined(FILTER_LINEAR)
+#if defined(FILTER_LINEAR) || defined(FILTER_SCREEN)
 uniform highp vec2 source_size;
 #endif
 
+#if defined(FILTER_SCREEN)
+uniform highp float scale;
+#endif
+
 varying highp vec2 varying_tex_coord;
 varying highp vec2 varying_tex_coord_min;
 varying highp vec2 varying_tex_coord_max;
@@ -142,6 +149,23 @@ void main(void) {
   vec4 color = mix(mix(c0, c1, rate.x), mix(c2, c3, rate.x), rate.y);
 #endif
 
+#if defined(FILTER_SCREEN)
+  pos = roundTexel(pos);
+  highp vec2 texel_size = 1.0 / source_size;
+  pos -= texel_size * 0.5 / scale;
+
+  highp vec2 p0 = pos;
+  highp vec2 p1 = pos + texel_size / scale;
+  vec4 c0 = texture2D(texture, p0);
+  vec4 c1 = texture2D(texture, vec2(p1.x, p0.y));
+  vec4 c2 = texture2D(texture, vec2(p0.x, p1.y));
+  vec4 c3 = texture2D(texture, p1);
+  // Texels must be in the source rect, so it is not necessary to check that like linear filter.
+
+  vec2 rate = min(max(1.0 - ((1.0 - fract(pos * source_size)) * scale), 0.0), 1.0);
+  vec4 color = mix(mix(c0, c1, rate.x), mix(c2, c3, rate.x), rate.y);
+#endif
+
   // Un-premultiply alpha
   if (0.0 < color.a) {
     color.rgb /= color.a;

internal/graphics/texture.go

@@ -24,6 +24,7 @@ const (
 	FilterDefault Filter = iota
 	FilterNearest
 	FilterLinear
+	FilterScreen
 )
 
 // texture represents OpenGL's texture.

internal/opengl/context_desktop.go

@@ -398,6 +398,14 @@ func (c *Context) UniformInt(p Program, location string, v int) {
 	})
 }
 
+func (c *Context) UniformFloat(p Program, location string, v float32) {
+	_ = c.runOnContextThread(func() error {
+		l := int32(c.locationCache.GetUniformLocation(c, p, location))
+		gl.Uniform1f(l, v)
+		return nil
+	})
+}
+
 func (c *Context) UniformFloats(p Program, location string, v []float32) {
 	_ = c.runOnContextThread(func() error {
 		l := int32(c.locationCache.GetUniformLocation(c, p, location))

internal/opengl/context_js.go

@@ -316,6 +316,12 @@ func (c *Context) UniformInt(p Program, location string, v int) {
 	gl.Uniform1i(l.(*js.Object), v)
 }
 
+func (c *Context) UniformFloat(p Program, location string, v float32) {
+	gl := c.gl
+	l := c.locationCache.GetUniformLocation(c, p, location)
+	gl.Uniform1f(l.(*js.Object), v)
+}
+
 func (c *Context) UniformFloats(p Program, location string, v []float32) {
 	gl := c.gl
 	l := c.locationCache.GetUniformLocation(c, p, location)

internal/opengl/context_mobile.go

@@ -309,6 +309,11 @@ func (c *Context) UniformInt(p Program, location string, v int) {
 	gl.Uniform1i(mgl.Uniform(c.locationCache.GetUniformLocation(c, p, location)), v)
 }
 
+func (c *Context) UniformFloat(p Program, location string, v float32) {
+	gl := c.gl
+	gl.Uniform1f(mgl.Uniform(c.locationCache.GetUniformLocation(c, p, location)), v)
+}
+
 func (c *Context) UniformFloats(p Program, location string, v []float32) {
 	gl := c.gl
 	l := mgl.Uniform(c.locationCache.GetUniformLocation(c, p, location))