feat(ggplot2): implement piano-roll-midi

plots/piano-roll-midi/implementations/r/ggplot2.R

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+#' anyplot.ai
+#' piano-roll-midi: MIDI Piano Roll Visualization
+#' Library: ggplot2 3.5.1 | R 4.4.1
+#' Quality: 89/100 | Created: 2026-06-03
+
+library(ggplot2)
+library(ragg)
+
+set.seed(42)
+
+# Theme tokens (Imprint palette)
+THEME       <- Sys.getenv("ANYPLOT_THEME", "light")
+PAGE_BG     <- if (THEME == "light") "#FAF8F1" else "#1A1A17"
+ELEVATED_BG <- if (THEME == "light") "#FFFDF6" else "#242420"
+INK         <- if (THEME == "light") "#1A1A17" else "#F0EFE8"
+INK_SOFT    <- if (THEME == "light") "#4A4A44" else "#B8B7B0"
+
+# Imprint sequential colormap for velocity: green (quiet) -> blue (loud)
+CMAP_LOW  <- "#009E73"
+CMAP_HIGH <- "#4467A3"
+
+# Piano keyboard row background colors
+KEY_WHITE <- if (THEME == "light") "#EBE7DC" else "#222220"
+KEY_BLACK <- if (THEME == "light") "#D3CDB8" else "#1D1D1B"
+
+NOTE_NAMES <- c("C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B")
+BLACK_KEYS <- c(1L, 3L, 6L, 8L, 10L)
+
+# --- Data: 8-measure C-major piano piece (32 beats, 4/4 time) ---------------
+
+# Right hand: eighth notes (0.5 beat each), melodic lines building to climax
+rh_pitches <- c(
+  60, 62, 64, 67, 69, 67, 64, 62,   # m1: gentle ascent/descent
+  60, 64, 67, 72, 71, 69, 67, 65,   # m2: arpeggiated C chord
+  64, 67, 69, 72, 74, 72, 69, 67,   # m3: E-based run
+  65, 67, 69, 72, 71, 72, 69, 67,   # m4: F-based figure
+  64, 67, 71, 72, 74, 76, 74, 72,   # m5: climbing higher
+  71, 72, 74, 76, 77, 79, 77, 76,   # m6: climax in upper register
+  74, 72, 71, 69, 67, 65, 64, 62,   # m7: long descent
+  60, 62, 64, 65, 64, 62, 60, 60    # m8: quiet resolution to C4
+)
+rh_starts    <- seq(0, 31.5, by = 0.5)
+rh_durations <- rep(0.45, 64L)
+
+# Velocity arc: mf start -> ff climax (m6) -> p resolution
+vel_raw <- c(
+  seq(55,  70, length.out = 8L),
+  seq(68,  82, length.out = 8L),
+  seq(80,  90, length.out = 8L),
+  seq(88,  95, length.out = 8L),
+  seq(93, 103, length.out = 8L),
+  seq(103, 118, length.out = 8L),
+  seq(112,  85, length.out = 8L),
+  seq(80,   48, length.out = 8L)
+)
+rh_vel <- pmin(pmax(round(vel_raw + rnorm(64L, 0, 4)), 30L), 127L)
+
+# Left hand: bass root on every quarter beat (C-F-Am-G progression, 2 measures each)
+bass_pitches <- rep(c(48L, 53L, 57L, 55L), each = 8L)
+bass_starts  <- 0:31
+bass_dur     <- rep(0.85, 32L)
+bass_vel     <- pmin(pmax(round(seq(62, 72, length.out = 32L) + rnorm(32L, 0, 3)), 30L), 100L)
+
+notes_df <- data.frame(
+  start    = c(rh_starts, as.numeric(bass_starts)),
+  end      = c(rh_starts + rh_durations, bass_starts + bass_dur),
+  pitch    = c(rh_pitches, bass_pitches),
+  velocity = c(rh_vel, bass_vel)
+)
+
+# Pitch range with 1-semitone margin
+pitch_min  <- min(notes_df$pitch) - 1L
+pitch_max  <- max(notes_df$pitch) + 1L
+all_pitches <- seq(pitch_min, pitch_max)
+
+# Separate background row data by key type
+white_rows <- all_pitches[!(all_pitches %% 12 %in% BLACK_KEYS)]
+black_rows <- all_pitches[  all_pitches %% 12 %in% BLACK_KEYS]
+
+bg_white <- data.frame(xmin = 0, xmax = 32, ymin = white_rows - 0.5, ymax = white_rows + 0.5)
+bg_black <- data.frame(xmin = 0, xmax = 32, ymin = black_rows - 0.5, ymax = black_rows + 0.5)
+
+# Y-axis: label only white keys
+y_labels <- paste0(NOTE_NAMES[(white_rows %% 12) + 1], floor(white_rows / 12) - 1)
+
+# Beat / measure grid positions (beat lines exclude measure boundaries)
+beat_xs    <- (1:31)[!(1:31 %% 4 == 0)]
+measure_xs <- seq(0L, 32L, by = 4L)
+
+# Climax highlight: measure 6 (beats 20-24) is the dynamic peak (ff)
+climax_df <- data.frame(xmin = 20, xmax = 24, ymin = pitch_min - 0.5, ymax = pitch_max + 0.5)
+
+plot_title <- "piano-roll-midi · r · ggplot2 · anyplot.ai"
+
+# --- Plot -------------------------------------------------------------------
+p <- ggplot() +
+  # Piano keyboard background: white keys
+  geom_rect(
+    data = bg_white,
+    aes(xmin = xmin, xmax = xmax, ymin = ymin, ymax = ymax),
+    fill = KEY_WHITE, color = NA
+  ) +
+  # Piano keyboard background: black keys
+  geom_rect(
+    data = bg_black,
+    aes(xmin = xmin, xmax = xmax, ymin = ymin, ymax = ymax),
+    fill = KEY_BLACK, color = NA
+  ) +
+  # Subtle translucent highlight at dynamic climax (m6, beats 20-24)
+  geom_rect(
+    data = climax_df,
+    aes(xmin = xmin, xmax = xmax, ymin = ymin, ymax = ymax),
+    fill = CMAP_HIGH, color = NA, alpha = 0.10
+  ) +
+  # Beat subdivision lines (very faint)
+  geom_vline(
+    xintercept = beat_xs,
+    color = INK_SOFT, linewidth = 0.12, alpha = 0.35
+  ) +
+  # Measure boundary lines (stronger)
+  geom_vline(
+    xintercept = measure_xs,
+    color = INK, linewidth = 0.4, alpha = 0.5
+  ) +
+  # MIDI notes colored by velocity
+  geom_rect(
+    data = notes_df,
+    aes(
+      xmin = start, xmax = end,
+      ymin = pitch - 0.42, ymax = pitch + 0.42,
+      fill = velocity
+    ),
+    color = PAGE_BG, linewidth = 0.15
+  ) +
+  # "ff" annotation marking the dynamic peak
+  annotate(
+    "text", x = 22, y = pitch_max - 0.3,
+    label = "ff", color = INK, size = 2.5, fontface = "bold.italic"
+  ) +
+  # Imprint sequential colormap for velocity (green=quiet, blue=loud)
+  scale_fill_gradient(
+    low    = CMAP_LOW,
+    high   = CMAP_HIGH,
+    limits = c(0, 127),
+    name   = "Velocity",
+    breaks = c(0, 32, 64, 96, 127),
+    labels = c("pp", "p", "mf", "f", "ff")
+  ) +
+  scale_x_continuous(
+    name   = "Measure",
+    breaks = seq(0, 32, by = 4),
+    labels = paste0("m", 1:9),
+    expand = expansion(add = c(0, 0))
+  ) +
+  scale_y_continuous(
+    name   = "Pitch",
+    breaks = white_rows,
+    labels = y_labels,
+    expand = expansion(add = c(0.5, 0.5))
+  ) +
+  labs(title = plot_title) +
+  theme_minimal(base_size = 8) +
+  theme(
+    plot.background   = element_rect(fill = PAGE_BG, color = PAGE_BG),
+    panel.background  = element_rect(fill = PAGE_BG, color = NA),
+    panel.grid.major  = element_blank(),
+    panel.grid.minor  = element_blank(),
+    panel.border      = element_rect(color = INK_SOFT, fill = NA, linewidth = 0.35),
+    axis.title        = element_text(color = INK,      size = 10),
+    axis.text         = element_text(color = INK_SOFT, size = 8),
+    axis.text.y       = element_text(color = INK_SOFT, size = 8),
+    plot.title        = element_text(color = INK,      size = 12, face = "bold"),
+    legend.background = element_rect(fill = ELEVATED_BG, color = INK_SOFT, linewidth = 0.3),
+    legend.text       = element_text(color = INK_SOFT, size = 8),
+    legend.title      = element_text(color = INK,      size = 9),
+    legend.position   = "right",
+    plot.margin       = margin(12, 12, 10, 10)
+  ) +
+  guides(
+    fill = guide_colorbar(
+      barheight = 12,
+      barwidth  = 0.8
+    )
+  )
+
+# --- Save -------------------------------------------------------------------
+ggsave(
+  filename = sprintf("plot-%s.png", THEME),
+  plot     = p,
+  device   = ragg::agg_png,
+  width    = 8,
+  height   = 4.5,
+  units    = "in",
+  dpi      = 400
+)