Open vs Merged GIF now uses disposals for better transitions (#40)

* white background works

* support gif disposals + background

cmd/ovm/animate.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"image"
+	"image/color"
+	"image/draw"
+	"image/gif"
+)
+
+func MakeGif(images []image.Image, delay int) gif.GIF {
+	// Alloc slice with 0 elems but capacity of all images
+	frames := make([]*image.Paletted, 0, len(images)+1)
+	delays := make([]int, 0, len(images)+1)
+	disposals := make([]byte, 0, len(images)+1)
+
+	for _, png := range images {
+		// Images are in reverse order so we need to prepend them
+		frames = append([]*image.Paletted{renderToPalette(png)}, frames...)
+		delays = append(delays, delay)
+		disposals = append(disposals, gif.DisposalBackground)
+	}
+
+	// Add out background to revert to when changing frames
+	frames = append([]*image.Paletted{makeBlank()}, frames...)
+	delays = append([]int{0}, delays...)
+	disposals = append([]byte{gif.DisposalNone}, disposals...)
+
+	return gif.GIF{
+		Image:           frames,
+		Delay:           delays,
+		LoopCount:       10,
+		Disposal:        disposals,
+		BackgroundIndex: 0,
+	}
+}
+
+func makeBlank() *image.Paletted {
+	var palette color.Palette = color.Palette{
+		image.Transparent,
+	}
+	img := image.NewPaletted(image.Rect(0, 0, 4025, 2048), palette)
+	draw.Draw(img, img.Bounds(), &image.Uniform{color.RGBA{0, 0, 0, 0}}, img.Bounds().Min, draw.Src)
+	return img
+}
+
+func renderToPalette(img image.Image) *image.Paletted {
+	var palette color.Palette = color.Palette{
+		image.Transparent,
+		// color.RGBA{255, 255, 255, 255},
+		color.RGBA{88, 166, 255, 255},
+		color.RGBA{63, 185, 80, 255},
+		color.RGBA{248, 81, 73, 255},
+		color.RGBA{163, 113, 247, 255},
+		color.RGBA{134, 94, 201, 255},
+	}
+	// Some days the images are off by a column so we are just hard coding the fix for now
+	// TODO(prince-chrismc) Make this more generic
+	sp := img.Bounds().Min
+	width := img.Bounds().Dx()
+	sp.X = width - 4025
+
+	paletted := image.NewPaletted(image.Rect(0, 0, 4025, 2048), palette)
+	draw.Draw(paletted, image.Rect(0, 0, 4025, 2048), img, sp, draw.Src)
+	return paletted
+}

cmd/ovm/dry_run.go

@@ -8,7 +8,6 @@ import (
 	"image/png"
 	"os"
 
-	"github.com/prince-chrismc/conan-center-index-pending-review/v2/internal/charts"
 	"github.com/wcharczuk/go-chart/v2"
 )
 
@@ -37,7 +36,7 @@ func SaveToDisk(barGraph chart.StackedBarChart, images []image.Image) error {
 	}
 
 	images = append([]image.Image{img}, images...)
-	jif := charts.MakeGif(images, delay)
+	jif := MakeGif(images, delay)
 
 	g, _ := os.Create("ovm.gif")
 	defer g.Close()

cmd/ovm/opened_versus_merged.go

@@ -92,7 +92,7 @@ func OpenVersusMerged(token string, dryRun bool) error {
 	}
 
 	images = append([]image.Image{img}, images...)
-	jif := charts.MakeGif(images, delay)
+	jif := MakeGif(images, delay)
 
 	var b3 bytes.Buffer
 	err = gif.EncodeAll(&b3, &jif)