mirror of
https://github.com/hajimehoshi/ebiten.git
synced 2024-12-26 11:48:55 +01:00
105 lines
3.3 KiB
Go
105 lines
3.3 KiB
Go
// Copyright 2018 The Ebiten Authors
|
|
//
|
|
// 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 (
|
|
"bytes"
|
|
"image"
|
|
_ "image/jpeg"
|
|
"log"
|
|
|
|
"github.com/hajimehoshi/ebiten/v2"
|
|
"github.com/hajimehoshi/ebiten/v2/examples/resources/images"
|
|
)
|
|
|
|
const (
|
|
screenWidth = 640
|
|
screenHeight = 480
|
|
)
|
|
|
|
var (
|
|
gophersImage *ebiten.Image
|
|
)
|
|
|
|
type Game struct{}
|
|
|
|
func (g *Game) Update() error {
|
|
return nil
|
|
}
|
|
|
|
func (g *Game) Draw(screen *ebiten.Image) {
|
|
op := &ebiten.DrawImageOptions{}
|
|
op.GeoM.Translate(0, 0)
|
|
screen.DrawImage(gophersImage, op)
|
|
|
|
// Box blur (7x7)
|
|
// https://en.wikipedia.org/wiki/Box_blur
|
|
//
|
|
// Note that this is a fixed function implementation of a box blur - more
|
|
// efficiency can be gained by using a separable blur
|
|
// (blurring horizontally and vertically separately, or for large blurs,
|
|
// even multiple horizontal or vertical passes), ideally combined with
|
|
// doing the summing up in a fragment shader (Kage can be used here).
|
|
//
|
|
// So this implementation only serves to demonstrate use of alpha blending.
|
|
layers := 0
|
|
for j := -3; j <= 3; j++ {
|
|
for i := -3; i <= 3; i++ {
|
|
op := &ebiten.DrawImageOptions{}
|
|
op.GeoM.Translate(float64(i), 244+float64(j))
|
|
// This is a blur based on the source-over blend mode,
|
|
// which is basically (GL_ONE, GL_ONE_MINUS_SRC_ALPHA). ColorM acts
|
|
// on unpremultiplied colors, but all Ebitengine internal colors are
|
|
// premultiplied, meaning this mode is regular alpha blending,
|
|
// computing each destination pixel as srcPix * alpha + dstPix * (1 - alpha).
|
|
//
|
|
// This means that the final color is affected by the destination color when BlendSourceOver is used.
|
|
// This blend mode is the default mode. See how this is calculated at the doc:
|
|
// https://pkg.go.dev/github.com/hajimehoshi/ebiten/v2#Blend
|
|
//
|
|
// So if using the same alpha every time, the end result will sure be biased towards the last layer.
|
|
//
|
|
// Correct averaging works based on
|
|
// Let A_n := (a_1 + ... + a_n) / n
|
|
// A_{n+1} = (a_1 + ... + a_{n+1}) / (n + 1)
|
|
// A_{n+1} = (n * A_n + a_{n+1)) / (n + 1)
|
|
// A_{n+1} = A_n * (1 - 1/(n+1)) + a_{n+1} * 1/(n+1)
|
|
// which is precisely what an alpha blend with alpha 1/(n+1) does.
|
|
layers++
|
|
op.ColorScale.ScaleAlpha(1 / float32(layers))
|
|
screen.DrawImage(gophersImage, op)
|
|
}
|
|
}
|
|
}
|
|
|
|
func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
|
|
return screenWidth, screenHeight
|
|
}
|
|
|
|
func main() {
|
|
// Decode an image from the image file's byte slice.
|
|
img, _, err := image.Decode(bytes.NewReader(images.FiveYears_jpg))
|
|
if err != nil {
|
|
log.Fatal(err)
|
|
}
|
|
gophersImage = ebiten.NewImageFromImage(img)
|
|
|
|
ebiten.SetWindowSize(screenWidth, screenHeight)
|
|
ebiten.SetWindowTitle("Blur (Ebitengine Demo)")
|
|
if err := ebiten.RunGame(&Game{}); err != nil {
|
|
log.Fatal(err)
|
|
}
|
|
}
|