Render covers with quadrant blocks for twice the horizontal detail

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -16,7 +16,7 @@ First release.
 - **Series drill-down:** seasons and episodes with monitoring, automatic search and release search.
 - **Downloads:** SABnzbd queue and history plus the Radarr and Sonarr queues; pause/resume, delete,
   retry, remove and blocklist.
-- **Posters:** thumbnails in the detail panes (half-block rendering, any color terminal).
+- **Posters:** thumbnails in the detail panes (quadrant block rendering, any color terminal).
 - **Log (F5) and popups:** feedback appears as fading popups; the log keeps the history.
 - Connection indicators for all three services, context-sensitive key hints, `?` help.
 - JSON config with environment overrides (`ARR_TUI_*`), `--version`, cross-platform builds

README.md

@@ -8,8 +8,8 @@ A terminal UI to search for movies and series with [Radarr](https://radarr.video
   optionally start the automatic search.
 - **Interactive search**: list the releases Radarr/Sonarr find (approved or rejected, with reasons),
   sort and filter them (by approval, quality, x265 / x264 / AV1, HDR, Dolby Vision, audio format, language), and grab one. Series: pick a season or a single episode first.
-- **Posters**: a small poster thumbnail in the detail panes, drawn with colored half-block
-  characters (needs a terminal with colors; works over SSH). Library items use the copy stored in
+- **Posters**: a small poster thumbnail in the detail panes, drawn with colored quadrant
+  block characters (needs a terminal with colors; works over SSH). Library items use the copy stored in
   Radarr/Sonarr; search results are downloaded from the metadata provider's image host
   (TMDb, TheTVDB). Turn it off with `"ui": {"covers": false}`.
 - **Library**: browse movies (top) and series (below) with a details pane on the right, filter by status (missing / downloaded / monitored) and by file properties (quality, x265 / x264 / AV1, HDR, Dolby Vision, audio format, language), toggle

SPECS.md

@@ -63,7 +63,7 @@ Notes:
   - Radarr and Sonarr queues (status, warnings, import errors), so stuck imports are visible.
   - Global speed / pause state in the status bar. Pause/resume and delete a SABnzbd job.
 - **Status bar / help:** the bottom bar lists the keys that work in the current view or panel; the top right shows the connection state of each service; `?` opens the full key reference.
-- **Posters:** the detail panes show a poster thumbnail above the text, rendered as half-block characters with 24-bit colors (each cell is two pixels; JPEG/PNG only, decoded and downscaled in the process, so no terminal graphics protocol is needed). Library items fetch `/MediaCover/<id>/poster-250.jpg` from their Radarr/Sonarr instance with the API key; search results fall back to the provider's `remoteUrl` (fetched without credentials). Posters are cached in memory, failed downloads are not retried for two minutes, and the poster shrinks or disappears when the pane is too short. `ui.covers: false` disables it.
+- **Posters:** the detail panes show a poster thumbnail above the text, rendered with quadrant block characters in 24-bit colors (each cell shows 2×2 pixels in the best two-color split, from the Block Elements range every font has; JPEG/PNG only, decoded and downscaled in the process, so no terminal graphics protocol is needed). Library items fetch `/MediaCover/<id>/poster-250.jpg` from their Radarr/Sonarr instance with the API key; search results fall back to the provider's `remoteUrl` (fetched without credentials). Posters are cached in memory, failed downloads are not retried for two minutes, and the poster shrinks or disappears when the pane is too short. `ui.covers: false` disables it.
 - **Notifications and log (F5):** feedback about actions (added, deleted, grabbed, failures) appears as popups in the bottom right that fade away (errors stay longer). Everything is also kept in the Log view; only connection changes of the background polling are logged, not every failed poll.
 
 ### 4.2 v0.2 (done, M8)

internal/ui/cover.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"fmt"
 	"image"
+	"image/color"
 	_ "image/jpeg" // poster formats
 	_ "image/png"
 	"time"
@@ -21,6 +22,7 @@ const (
 	coverFailureTTL   = 2 * time.Minute
 	maxCoverCache     = 300
 	coverFetchLimit   = 4
+	flatCellError     = 600 // squared RGB distance below which a cell is drawn flat
 )
 
 // decodeCover decodes a JPEG or PNG poster and keeps a small copy.
@@ -68,9 +70,11 @@ func boxScale(src image.Image, w, h int) *image.RGBA {
 	return dst
 }
 
-// coverView draws a poster with half-block characters: every cell shows two
-// vertically stacked pixels (foreground = upper, background = lower), so it
-// works in any terminal with colors, also over SSH.
+// coverView draws a poster with quadrant block characters: every cell shows
+// 2×2 pixels in two colors (the best split of the four pixels into a
+// foreground and a background group), which doubles the horizontal detail of
+// plain half blocks. The glyphs are all from the Block Elements range that
+// every terminal font has, and it works over SSH.
 type coverView struct {
 	*tview.Box
 	img  *image.RGBA
@@ -84,6 +88,18 @@ func newCoverView() *coverView { return &coverView{Box: tview.NewBox()} }
 func (c *coverView) setImage(img *image.RGBA) { c.img, c.note, c.scaled = img, "", nil }
 func (c *coverView) setNote(note string)      { c.img, c.note, c.scaled = nil, note, nil }
 
+// coverCells returns how many columns and rows a poster of the given aspect
+// needs inside w×h cells. A cell is about twice as tall as it is wide.
+func coverCells(imgW, imgH, w, h int) (cols, rows int) {
+	cols = w
+	rows = cols * imgH / imgW / 2
+	if rows > h {
+		rows = h
+		cols = rows * 2 * imgW / imgH
+	}
+	return max(cols, 0), max(rows, 0)
+}
+
 func (c *coverView) Draw(screen tcell.Screen) {
 	c.Box.DrawForSubclass(screen, c)
 	x, y, w, h := c.GetInnerRect()
@@ -97,33 +113,92 @@ func (c *coverView) Draw(screen tcell.Screen) {
 		return
 	}
 
-	// Fit the poster into w columns by 2h pixel rows, keeping its aspect.
 	b := c.img.Bounds()
-	tw := w
-	th := tw * b.Dy() / b.Dx()
-	if th > 2*h {
-		th = 2 * h
-		tw = th * b.Dx() / b.Dy()
-	}
-	th &^= 1
-	if tw < 1 || th < 2 {
+	cols, rows := coverCells(b.Dx(), b.Dy(), w, h)
+	if cols < 1 || rows < 1 {
 		return
 	}
-	if c.scaled == nil || c.scaled.Bounds().Dx() != tw || c.scaled.Bounds().Dy() != th {
-		c.scaled = boxScale(c.img, tw, th)
+	if c.scaled == nil || c.scaled.Bounds().Dx() != 2*cols || c.scaled.Bounds().Dy() != 2*rows {
+		c.scaled = boxScale(c.img, 2*cols, 2*rows)
 	}
-	px := func(px, py int) tcell.Color {
-		i := c.scaled.PixOffset(px, py)
-		return tcell.NewRGBColor(int32(c.scaled.Pix[i]), int32(c.scaled.Pix[i+1]), int32(c.scaled.Pix[i+2]))
+	px := func(x, y int) color.RGBA {
+		i := c.scaled.PixOffset(x, y)
+		return color.RGBA{c.scaled.Pix[i], c.scaled.Pix[i+1], c.scaled.Pix[i+2], 255}
 	}
-	for row := 0; row < th/2; row++ {
-		for col := 0; col < tw; col++ {
-			style := tcell.StyleDefault.Foreground(px(col, 2*row)).Background(px(col, 2*row+1))
-			screen.SetContent(x+col, y+row, '▀', nil, style)
+	for row := 0; row < rows; row++ {
+		for col := 0; col < cols; col++ {
+			ch, fg, bg := quadCell([4]color.RGBA{
+				px(2*col, 2*row), px(2*col+1, 2*row), // top left, top right
+				px(2*col, 2*row+1), px(2*col+1, 2*row+1), // bottom left, bottom right
+			})
+			style := tcell.StyleDefault.Foreground(tcell.NewRGBColor(int32(fg.R), int32(fg.G), int32(fg.B))).
+				Background(tcell.NewRGBColor(int32(bg.R), int32(bg.G), int32(bg.B)))
+			screen.SetContent(x+col, y+row, ch, nil, style)
 		}
 	}
 }
 
+// quadrants[mask] is the glyph that fills the quadrants set in mask
+// (bit 0 top left, 1 top right, 2 bottom left, 3 bottom right).
+var quadrants = [16]rune{' ', '▘', '▝', '▀', '▖', '▌', '▞', '▛', '▗', '▚', '▐', '▜', '▄', '▙', '▟', '█'}
+
+// quadCell picks the glyph and colors that best reproduce four pixels (top
+// left, top right, bottom left, bottom right) with one foreground and one
+// background color.
+func quadCell(p [4]color.RGBA) (ch rune, fg, bg color.RGBA) {
+	mean := func(mask int, want bool) (c [3]float64, n int) {
+		for i := 0; i < 4; i++ {
+			if (mask>>i&1 == 1) == want {
+				c[0], c[1], c[2] = c[0]+float64(p[i].R), c[1]+float64(p[i].G), c[2]+float64(p[i].B)
+				n++
+			}
+		}
+		for k := range c {
+			if n > 0 {
+				c[k] /= float64(n)
+			}
+		}
+		return c, n
+	}
+	// err is the squared distance of the pixels in one group to the group's mean.
+	errOf := func(mask int, want bool, m [3]float64) (e float64) {
+		for i := 0; i < 4; i++ {
+			if (mask>>i&1 == 1) == want {
+				dr, dg, db := float64(p[i].R)-m[0], float64(p[i].G)-m[1], float64(p[i].B)-m[2]
+				e += dr*dr + dg*dg + db*db
+			}
+		}
+		return e
+	}
+	toRGBA := func(m [3]float64) color.RGBA {
+		return color.RGBA{uint8(m[0] + .5), uint8(m[1] + .5), uint8(m[2] + .5), 255}
+	}
+
+	// Mask 0 is a single flat color. A split must clearly beat it, and nearly
+	// flat cells (smooth gradients, noise) stay flat. Only masks without the
+	// bottom right quadrant are tried: a mask and its complement draw the same
+	// picture with swapped colors.
+	flat, _ := mean(0, false)
+	flatErr := errOf(0, false, flat)
+	best, bestErr := 0, flatErr*0.6
+	if flatErr >= flatCellError {
+		for mask := 1; mask < 8; mask++ {
+			fm, _ := mean(mask, true)
+			bm, _ := mean(mask, false)
+			if e := errOf(mask, true, fm) + errOf(mask, false, bm); e < bestErr {
+				best, bestErr = mask, e
+			}
+		}
+	}
+	if best == 0 {
+		c := toRGBA(flat)
+		return ' ', c, c
+	}
+	fm, _ := mean(best, true)
+	bm, _ := mean(best, false)
+	return quadrants[best], toRGBA(fm), toRGBA(bm)
+}
+
 // coverRef says where a poster comes from. The zero value means "no poster".
 type coverRef struct {
 	key   string // identifies the poster in the cache

internal/ui/cover_test.go

@@ -77,39 +77,80 @@ func TestDecodeCover(t *testing.T) {
 	}
 }
 
-func TestCoverViewDrawsHalfBlocks(t *testing.T) {
+func TestQuadCell(t *testing.T) {
+	red, blue, black := color.RGBA{255, 0, 0, 255}, color.RGBA{0, 0, 255, 255}, color.RGBA{0, 0, 0, 255}
+	for _, tc := range []struct {
+		name     string
+		px       [4]color.RGBA
+		wantCh   rune
+		wantFg   color.RGBA
+		wantBg   color.RGBA
+		sameBoth bool
+	}{
+		{"flat", [4]color.RGBA{red, red, red, red}, ' ', red, red, true},
+		{"top half", [4]color.RGBA{red, red, blue, blue}, '▀', red, blue, false},
+		{"bottom half", [4]color.RGBA{blue, blue, red, red}, '▀', blue, red, false}, // same picture, canonical form
+		{"left half", [4]color.RGBA{red, blue, red, blue}, '▌', red, blue, false},
+		{"one corner", [4]color.RGBA{red, blue, blue, blue}, '▘', red, blue, false},
+		{"diagonal", [4]color.RGBA{red, black, black, red}, '▞', black, red, false},
+	} {
+		ch, fg, bg := quadCell(tc.px)
+		if ch != tc.wantCh || fg != tc.wantFg || bg != tc.wantBg {
+			t.Errorf("%s: %q fg=%v bg=%v, want %q fg=%v bg=%v", tc.name, ch, fg, bg, tc.wantCh, tc.wantFg, tc.wantBg)
+		}
+	}
+	// Nearly flat noise stays a flat cell instead of a distracting pattern.
+	n := color.RGBA{100, 100, 100, 255}
+	m := color.RGBA{102, 100, 101, 255}
+	if ch, _, _ := quadCell([4]color.RGBA{n, m, n, n}); ch != ' ' {
+		t.Errorf("noise rendered as %q", ch)
+	}
+}
+
+func TestCoverCells(t *testing.T) {
+	// A 2:3 poster in a roomy box is limited by the height: 10 rows are 20
+	// width units tall, so 13 columns.
+	if c, r := coverCells(40, 60, 30, 10); c != 13 || r != 10 {
+		t.Errorf("tall limit: %dx%d", c, r)
+	}
+	// In a narrow box the width limits it.
+	if c, r := coverCells(40, 60, 10, 20); c != 10 || r != 7 {
+		t.Errorf("narrow limit: %dx%d", c, r)
+	}
+}
+
+func TestCoverViewDraws(t *testing.T) {
 	screen := tcell.NewSimulationScreen("")
 	if err := screen.Init(); err != nil {
 		t.Fatal(err)
 	}
 	defer screen.Fini()
-	screen.SetSize(20, 10)
+	screen.SetSize(30, 10)
 
 	c := newCoverView()
-	c.setImage(stripes(40, 60)) // 2:3 poster
-	c.SetRect(0, 0, 20, 10)     // 20 columns × 20 pixel rows: a 13×20 pixel poster
-	c.Draw(screen)
+	c.setImage(stripes(40, 60)) // red above blue
+	c.SetRect(0, 0, 30, 10)     // fits 13 columns × 10 rows
 
-	// Row 0 holds pixel rows 0 (top) and 1: both red. The middle cell row
-	// (index 4/5) crosses into blue; the last row is blue on both halves.
+	c.Draw(screen)
 	rgba := func(c tcell.Color) color.RGBA {
 		r, g, b := c.RGB()
 		return color.RGBA{uint8(r), uint8(g), uint8(b), 255}
 	}
-	check := func(row int, wantFg, wantBg color.RGBA) {
-		t.Helper()
-		ch, _, style, _ := screen.GetContent(0, row)
-		fg, bg, _ := style.Decompose()
-		if ch != '▀' || rgba(fg) != wantFg || rgba(bg) != wantBg {
-			t.Errorf("row %d: %q fg=%v bg=%v", row, ch, rgba(fg), rgba(bg))
-		}
+	cell := func(x, y int) (rune, color.RGBA, color.RGBA) {
+		ch, _, st, _ := screen.GetContent(x, y)
+		fg, bg, _ := st.Decompose()
+		return ch, rgba(fg), rgba(bg)
 	}
 	red, blue := color.RGBA{255, 0, 0, 255}, color.RGBA{0, 0, 255, 255}
-	check(0, red, red)
-	check(9, blue, blue)
-	// Beyond the poster's width nothing is drawn.
-	if ch, _, _, _ := screen.GetContent(19, 0); ch == '▀' {
-		t.Error("poster stretched beyond its aspect ratio")
+	if _, fg, bg := cell(0, 0); fg != red || bg != red {
+		t.Errorf("top row = fg %v bg %v, want red", fg, bg)
+	}
+	if _, fg, bg := cell(12, 9); fg != blue || bg != blue {
+		t.Errorf("bottom right = fg %v bg %v, want blue", fg, bg)
+	}
+	// Outside the poster's footprint nothing is drawn.
+	if ch, _, _, _ := screen.GetContent(13, 0); ch != ' ' {
+		t.Errorf("poster stretched beyond its aspect ratio: %q", ch)
 	}
 }
 

internal/ui/detail.go

@@ -8,7 +8,7 @@ import (
 )
 
 const (
-	coverRows    = 18 // poster height in terminal rows (36 pixels)
+	coverRows    = 20 // poster height in terminal rows
 	minCoverRows = 6  // a smaller poster is not worth showing
 	minTextRows  = 10 // the poster never takes these rows from the text
 )