tview

Publication-quality alignment viewer for nucleotide and amino acid sequences. A lightweight alternative to samtools tview that produces clean, stable image output.

Supports BAM files (with reference FASTA), pre-aligned FASTA (e.g. MAFFT output), and stacking multiple inputs into a single figure.

BAM mode — SNP (yellow), 3bp deletion, 2bp insertion (purple columns), reverse-strand insertion

FASTA mode — HIV Env protein alignment (HxB2 reference), amino acid palette

Stacked mode — two BAM files sharing a reference and region

Classic mode — black-and-white rendering for textbook-style figures and grayscale print

Dual-reference mode — variant calls against SF162p3_ref (bottom row + bottom x-axis) with HxB2 numbering (top row + top x-axis). Different gap patterns mean position 10 on each axis lands in a different alignment column.

---

Installation

pip install tview

Installs matplotlib, click, and pysam.

---

Quick Start

BAM file

tview \
  --bam aligned.bam \
  --ref reference.fa \
  --region chr1:100-200 \
  -o alignment.png

Aligned FASTA (e.g. MAFFT output)

The first sequence in the file is treated as the reference.

tview \
  --fasta env_protein_aligned.fasta \
  --palette aa \
  -o env_alignment.png

Subset columns from a FASTA alignment

Use --columns with 1-based inclusive range to window into long alignments.

tview \
  --fasta aligned.fasta \
  --columns 1-120 \
  --palette aa \
  -o first_120_cols.png

Classic (black-and-white) mode

Use --classic-mode for textbook-style monochrome output — all black text on a white background with no colored highlighting. Structural conventions (. , lowercase, -) are preserved.

tview \
  --fasta aligned.fasta \
  --palette aa \
  --classic-mode \
  -o classic_output.png

---

Dual Reference (Heterologous MSA)

For heterologous MSAs (e.g. HIV with HxB2 + multiple strains + reads), the variant-call reference and the x-axis numbering reference do not have to be the same sequence. --variant-ref selects the FASTA header against which mismatches are colored; --numbering-ref selects the FASTA header whose non-gap positions label the x-axis.

When both are set and differ:

• Both refs render as rows at the top (numbering ref first, variant ref second).
• A second x-axis is drawn at the bottom of the figure for the variant-ref's coordinates.
• The top axis carries the numbering ref's coordinates with a (<numbering_ref>) annotation; the bottom axis carries the variant ref's coordinates with a (<variant_ref>) annotation.
• Per-row labels are auto-enabled so you can tell the two top rows apart.
• --max-rows N counts samples only — references are always shown.

tview \
  --fasta env_protein_aligned.fasta \
  --palette aa \
  --columns 1-60 \
  --variant-ref SF162p3_ref \
  --numbering-ref HxB2 \
  --max-rows 6 \
  -o env_dual_ref.png

Gap patterns differ between strains — HxB2 position 10 and SF162p3_ref position 10 typically land on different alignment columns. That's the point: both axes complement each other.

Per-row labels

Show sequence IDs to the left of each row (auto-enabled in dual-ref mode):

tview --fasta aligned.fasta --show-row-labels -o labeled.png

Tick frequency

Default labels are placed at non-gap positions 1, 10, 20, 30, ... Use --tick-every N to change the interval. --tick-every 1 labels every column — useful for short alignments or when exact position readout matters.

tview \
  --fasta env_protein_aligned.fasta \
  --variant-ref SF162p3_ref --numbering-ref HxB2 \
  --columns 1-60 --max-rows 6 \
  --tick-every 1 \
  -o env_dual_ref_per_column.png

---

Stacking Multiple Panels

Each input file becomes a vertically stacked panel separated by a thin line. Panels are labeled on the left with the filename stem.

Multiple BAMs (shared reference and region)

tview \
  --bam sample1.bam --bam sample2.bam --bam sample3.bam \
  --ref reference.fa \
  --region chr1:100-200 \
  -o stacked.png

Multiple FASTAs

tview \
  --fasta group1_aligned.fasta --fasta group2_aligned.fasta \
  --palette aa \
  --columns 1-120 \
  -o comparison.png

Mix BAM and FASTA panels

--ref and --region apply only to BAM panels; --columns applies only to FASTA panels.

tview \
  --bam reads.bam \
  --ref reference.fa \
  --region chr1:100-200 \
  --fasta protein_aligned.fasta \
  --columns 1-120 \
  -o mixed.png

BAM panels are rendered first (top), FASTA panels below.

---

Piping from stdin

Pass - to read file paths from stdin (one per line). Each path becomes its own panel.

# find → stacked panels
find ./alignments -name "*.fasta" -type f | \
  tview --fasta - --palette aa --columns 1-120 -o all.png

# ls with pattern
ls samples/*.bam | \
  tview --bam - --ref ref.fa --region chr1:100-200 -o all_samples.png

# single file via echo
echo "my_alignment.fasta" | \
  tview --fasta - --palette aa -o out.png

---

Python API

The core functions are available as a Python library:

from tview import fasta_panel, bam_panel, render_panels

# FASTA alignment
panel = fasta_panel("aligned.fasta", columns=list(range(1, 121)))
render_panels([panel], "output.png", palette="aa")

# BAM alignment
panel = bam_panel("sample.bam", "reference.fa", "chr1:100-200")
render_panels([panel], "output.png")

# Stack multiple panels
panels = [
    bam_panel("sample1.bam", "ref.fa", "chr1:100-200"),
    bam_panel("sample2.bam", "ref.fa", "chr1:100-200"),
]
render_panels(panels, "stacked.png", dpi=300, fontsize=7, cell=0.14)

# Classic (black-and-white) mode
panel = fasta_panel("aligned.fasta")
render_panels([panel], "classic.png", palette="aa", classic=True)

# Dual-reference: variant calls against SF162p3, x-axis numbered by HxB2
panel = fasta_panel(
    "env_protein_aligned.fasta",
    columns=list(range(1, 61)),
    variant_ref="SF162p3_ref",
    numbering_ref="HxB2",
    max_rows=6,
)
render_panels([panel], "dual_ref.png", palette="aa", show_row_labels=True)

# Per-column tick labels
panel = fasta_panel("aligned.fasta", tick_every=1)
render_panels([panel], "per_col.png", palette="aa")

# Heterologous orange highlight (separate from dual-ref)
# Sample bases that mismatch ref_row but match secondary_ref_row render in orange + bold.
from tview.models import Panel
panel = fasta_panel("aligned.fasta")
panel = Panel(
    label=panel.label,
    ref_row=panel.ref_row,
    seq_rows=panel.seq_rows,
    total_cols=panel.total_cols,
    col_labels=panel.col_labels,
    secondary_ref_row=list("..."),  # other strain aligned to same grid
)
render_panels([panel], "hetero.png", palette="aa")

---

Composing with patchworklib

draw_panels() and panel_figsize() let you draw alignments onto any matplotlib axes, including patchworklib Brick objects for composing multi-panel figures.

pip install patchworklib
# or
pip install tview[compose]

import patchworklib as pw
from tview import fasta_panel, draw_panels, panel_figsize

# Build alignment panel
panel = fasta_panel("aligned.fasta", columns=list(range(1, 121)))
w, h = panel_figsize([panel], fontsize=7, cell=0.14)

# Draw onto a patchworklib Brick
alignment = pw.Brick(label="alignment", figsize=(w, h))
draw_panels([panel], ax=alignment, fontsize=7, palette="aa", cell=0.14)

# Compose with other plots
scatter = pw.Brick(label="scatter", figsize=(3, 3))
scatter.scatter([1, 2, 3], [4, 5, 6])

layout = alignment / scatter   # vertical stack
layout.savefig("composed.png")

This also works with standard matplotlib subplots:

import matplotlib.pyplot as plt
from tview import fasta_panel, draw_panels, panel_figsize

panel = fasta_panel("aligned.fasta")
w, h = panel_figsize([panel])
fig, (ax1, ax2) = plt.subplots(1, 2, figsize=(w + 4, max(h, 3)))

draw_panels([panel], ax1, palette="aa")
ax2.scatter([1, 2, 3], [4, 5, 6])

plt.tight_layout()
plt.savefig("side_by_side.png", dpi=300, bbox_inches="tight")

---

Visual Conventions

Element	Symbol	Style
Match (forward)	.	light grey
Match (reverse)	,	light grey, reduced opacity
Mismatch	A T etc.	colored, yellow highlight, bold
Mismatch (reverse)	a t etc.	lowercase, colored, yellow highlight
Heterologous match	A T etc.	orange #FF6F00, bold, yellow highlight (mismatches ref_row but matches secondary_ref_row)
Deletion	-	grey dash
Insertion	colored bases	purple column shading
Gap (ref in insertion col)	-	grey dash
Gap (FASTA alignment)	-	grey dash

---

Color Palettes

--palette nt (default) — Nucleotides

Base	Color
A	green #4CAF50
C	blue #2196F3
G	orange #FF9800
T	red #F44336

--palette aa — Amino Acids (Clustal-inspired)

Group	Residues	Color
Hydrophobic	A V L I M F W P	blue #2196F3
Positive charge	K R H	red #F44336
Negative charge	D E	magenta #E040FB
Polar uncharged	S T N Q	green #4CAF50
Special	G C Y	orange #FF9800

---

Full Argument Reference

Usage: tview [OPTIONS]

  Publication-quality alignment viewer (BAM or FASTA).

Options:
  --bam TEXT              BAM file(s) — each becomes a panel. Use '-' for stdin.
  --ref PATH              Reference FASTA (required for BAM mode).
  --region TEXT            Genomic region chr:start-end (required for BAM mode).
  --fasta TEXT             Aligned FASTA file(s) — each becomes a panel. Use '-' for stdin.
  --columns TEXT           Column positions for FASTA, 1-based (e.g. 1-120, 5,40,690, or 5,10-20,40).
  -o, --output TEXT        Output image path.  [default: alignment.png]
  --palette [nt|aa]        Color palette.  [default: nt]
  --dpi INTEGER            Image resolution.  [default: 300]
  --fontsize INTEGER       Base font size in points.  [default: 7]
  --cell FLOAT             Cell size in inches.  [default: 0.14]
  --classic-mode           Black-and-white rendering with no color highlighting.
  --show                   Display rendered image inline via 'kitten icat' (Kitty/Ghostty).
  --max-rows INTEGER       Cap sample rows (FASTA) or reads (BAM) per panel.
  --variant-ref TEXT       FASTA header for variant calling (mismatches drawn against this).
  --numbering-ref TEXT     FASTA header for x-axis numbering. Renders as second top row + bottom axis when different from --variant-ref.
  --show-row-labels        Show sequence ID labels on the left of each row.
  --tick-every INTEGER     Label every Nth x-axis position. Use 1 for every column.  [default: 10]
  -h, --help               Show this message and exit.

Argument	Description	Default
--bam	BAM file(s), each becomes a panel. Use - for stdin.	—
--ref	Reference FASTA (required for BAM mode)	—
--region	Genomic region chr:start-end (required for BAM)	—
--fasta	Aligned FASTA file(s), each becomes a panel. Use - for stdin.	—
--columns	Column positions for FASTA, 1-based. Supports 1-120, 5,40,690, or 5,10-20,40.	full alignment
-o, --output	Output image path	alignment.png
--palette	Color palette: nt or aa	nt
--dpi	Image resolution	300
--fontsize	Base font size in points	7
--cell	Cell size in inches (controls spacing)	0.14
--classic-mode	Black-and-white rendering with no color highlighting	False
--show	Display via kitten icat (Kitty/Ghostty)	False
--max-rows	Cap sample rows (FASTA) or reads (BAM) per panel. In dual-ref mode, refs are always shown.	—
--variant-ref	(FASTA) Header name used as variant-call reference. Mismatches drawn against this row.	first sequence
--numbering-ref	(FASTA) Header name used for x-axis numbering. Renders as second top row + bottom axis when different from --variant-ref.	same as --variant-ref
--show-row-labels	Show sequence ID labels on the left of each row. Auto-enabled when --variant-ref and --numbering-ref differ.	False
--tick-every	Label every Nth x-axis position. Use 1 to label every column.	10

---

Tips for Publication Figures

• Use --dpi 300 (default) for print, --dpi 150 for drafts.
• Use --cell 0.10 for denser layouts with many sequences, --cell 0.18 for fewer.
• Use --fontsize 5 or 6 when displaying wide alignments (>100 columns).
• The output format is determined by the file extension: .png, .pdf, .svg all work.
• For Nature-style figures, .pdf or .svg output preserves vector text.
• Use --classic-mode for textbook-style monochrome figures that reproduce well in grayscale print.

# Vector output for publication
tview \
  --fasta aligned.fasta \
  --palette aa \
  --columns 1-120 \
  --cell 0.12 \
  --fontsize 6 \
  -o figure_2a.pdf

---

FASTA Input Format

The FASTA input must be pre-aligned (e.g. by MAFFT, MUSCLE, Clustal). The first sequence is used as the reference for comparison. Gap characters (-) in the alignment are preserved and rendered as grey dashes.

>HxB2_reference
MRVK---EKYQHLWRWGWRWGTMLLGMLMICS...
>sample_001
MRVKGIRKNAQHL----WRGGTLLLGMLMICS...
>sample_002
--------------------------MLMICS...

The x-axis labels count non-gap positions in the reference sequence (1, 10, 20, ...) so position numbers always correspond to the reference residue numbering regardless of gap columns. The interval is configurable via --tick-every N.

Pass --variant-ref <name> to pick a non-first sequence as the reference for variant calling. Pass --numbering-ref <name> to layer a second reference whose non-gap positions drive an additional x-axis (typical HIV use case: HxB2 numbering with variant calls against a different strain).