SpectraLab

A pure JavaScript viewer and editor for ZX Spectrum graphics formats. No server required — runs directly in any browser, locally or hosted. No build system, no bundler, no framework.

Features

• View a wide range of ZX Spectrum screen formats (standard, multicolor, ULA+, ULANext, Gigascreen, tricolor RGB, SPECSCII, chr$, Nirvana tiles, MGH, HLR, STL, BSP, NXI, SL2, etc.)
• Edit SCR, ULA+, ULANext, 53c/127c, BSC, BSP, BMC4, IFL, MLT, Gigascreen, RGB3, SPECSCII, chr$, ZXP, MGH (mg1/mg2/mg4/mg8), HLR, STL, NXI and SL2 pictures with pixel-accurate tools
• Multi-picture editing: open and edit up to 15 pictures simultaneously with tab switching, per-picture undo, layers and zoom
• Workspace files: save/load all open pictures as a single .slw file (palette, filters, grid, reference image, sprite sheet, etc.)
• Project files: save a single picture with full layers/attributes/border/mask data as .slp
• Import PNG/GIF/JPG/WebP/BMP images with dithering, LAB color space matching, alignment controls and conversion to any editable format
• Import animated GIF directly as SCA animation — multi-frame GIFs are auto-detected, each frame converted to SCR with dithering, per-frame delays preserved
• Tile to screens: split a large image into a grid of output-format-sized pictures with automatic edge padding
• Sprite editor: floating multi-tile sprite sheet editor with mono / attributed / multicolour (8×1, 8×2, 8×4) modes, animation, onion skinning, grab from screen/memory, Nirvana .btile/.wtile export
• Load .sna and .z80 snapshots (48K and 128K, V1/V2/V3) and extract screens and sprites from snapshot RAM
• Memory Viewer: browse any memory bank as 1-bit graphics with sprite extraction, multiple addressing/grab modes
• Play SCA animations (type 0 full frames and type 1 attribute-only) with frame-by-frame control
• Edit SCA animations: trim, adjust delays, remove duplicates, export to SCA / SCR zip / 53c zip / animated GIF / PNG zip
• Customize display: fractional / x1–x20 zoom, border color/size, palettes (including 53c/127c pattern-blended palettes, ULA+ 64-color), grid and subgrid overlays (separate for paper/border), grid color presets, monochrome mode, flash animation
• Display filters: CRT scanlines, noise, composite chroma bleed, phosphor glow, vignette, CRT curvature, pixel smoothing, with built-in presets (CRT TV, Composite, VHS, Arcade)
• Fullscreen mode (F11) with floating tool palette in both viewer and editor
• Tabbed UI: View (display + filters), Edit (drawing tools + layers), Transform (undo / save / convert / workspace)
• Load files directly from ZIP archives (auto-extract) and drag-and-drop anywhere on the window
• Custom fonts for SPECSCII and Text tool (768/ch8 ZX Spectrum fonts plus TrueType/OpenType)
• Export to PNG/GIF: export any screen to PNG or animated GIF (gigascreen flicker) using current view settings (zoom, border, grid, palette, filters)
• QR code generator: V1–V20, module sizes 1/2/3/4/8, grid-snapped placement
• Dark / light theme (follows OS preference on first visit)

Screen Editor

Edit SCR, ULA+, ULANext, BSC, BSP, BMC4, IFL, MLT, Gigascreen, RGB3, 53c/127c, SPECSCII, ZXP, chr$, MGH, HLR, STL, NXI and SL2 pictures with authentic ZX Spectrum color handling:

• Tools: Pixel (P), Line (L), Rectangle (R), Circle/Ellipse (O), Airbrush (G), Gradient (D), Flood Fill (I), Fill Cell (C), Recolor (A), Eraser (E), Text (T), Select (S), Color Picker (K)
• Eraser (E): makes pixels transparent on upper layers; paints paper on background
• Airbrush (G): sprays random pixels within a radius
  • Configurable radius (4–32px), density (0.03–1.0), falloff (Uniform → Very Hard)
  • Supports all brush paint modes including masked stencil modes
  • Continuous spray while mouse button held; path-distributed spray at high speeds
• Gradient (D): fills with dithered monochrome gradients
  • Types: Linear, Radial, Diamond, Conical, Square, Spiral
  • Dithering: Bayer 8×8 or blue noise 16×16
  • Supports custom brushes and all paint modes
• Color Picker (K): dedicated eyedropper tool, or Alt+click in any drawing tool
  • Works on SCR, BSC, BSP, IFL, MLT, BMC4, ULA+, Gigascreen, STL, 53c/127c, RGB3, NXI, SL2, SPECSCII
  • Left click picks ink/primary, right click picks paper/secondary
• Fill with patterns: Flood Fill uses the selected brush — custom brush patterns tile across the fill area for dithered fills
• Brush: sizes 1–16px, shapes Square / Round / Horizontal / Vertical / Stroke (/) / Back stroke () — applies to Pixel, Line, Rectangle, Circle, Eraser, Fill, Airbrush
• Brush paint modes: Replace (default), Set, Invert, Recolor, Retouch, Masked, Masked+ — persisted to localStorage
• Custom Brushes & Tilesets: tabbed interface with Custom, ROM, UDG, and user-loaded tabs
  • Custom tab: 12 user brush slots, capture from screen (max 64×64)
    • Click = select, Shift+click = capture, Ctrl+click = clear
    • Rotate 90° CW (R), Mirror H (H), Mirror V (V)
  • ROM tab: current font as 96 selectable 8×8 tiles
  • UDG tab: 96 built-in tiles (block graphics, dithers, borders, shapes, arrows, connectors)
  • Load tilesets via "+" button: 768-byte (96 tiles) or 2048-byte (256 tiles) formats, or .slb brush sets
  • Grab tileset from screen via crosshair: select area, tiles grabbed L→R, T→B
  • Click any tile to use as brush with all drawing tools
  • Up to 8 tabs total; user tabs persist in localStorage
• Copy/Paste: Select tool (S) drag-selects (auto-copies); Ctrl+V to paste with preview
  • Snap modes: Grid, Grid Center, Subgrid, Subgrid Center, Zero, Brush, Off
  • Paste respects brush paint mode; rotate / mirror clipboard during paste
• Layers: add/remove/reorder with visibility toggles, per-layer attributes (all formats except attribute-only)
  • Background layer always opaque, upper layers support transparency via eraser
  • Attribute compositing per cell from topmost visible layer that has pixel content
  • Layers include per-layer border data for BSC/BMC4
  • Flatten merges all layers into the background
  • Add/remove/move/flatten are undoable
• Drawing: Left click = ink, Right click = paper
• Colors: ink (0–7), paper (0–7), Bright and Flash toggles; persisted ink/paper across sessions
• Undo/Redo: 32 levels (Ctrl+Z / Ctrl+Y) with full state restoration (format, filename, ULA+ palette, layers, masks, HLR pattern, etc.)
• Preview panel: draggable, zoomable (x1–x4), shows full screen while editing
• Text tool: ZX Spectrum .768/.ch8 bitmap fonts or TrueType/OpenType fonts at any size
• QR code generator: V1–V20 (20–970 characters), module sizes 1/2/3/4/8px, grid-snapped placement, live preview
• Fullscreen mode (F11): maximizes canvas with floating tool palette (Tab toggles palette)
• Save: export back to the original format (Ctrl+S); layers are automatically flattened
• Format conversion: SCR ↔ ATTR ↔ BSC ↔ BSP, SCR/ULA+ → NXI/SL2 (256/320/640), NXI ↔ SL2, NXI/SL2 cross-mode (256↔320↔640), NXI/SL2 → SCR; border color picker, 18 bitmap patterns for attr→bitmap
• Multi-picture tab bar: appears with 2+ pictures, independent undo/layers/zoom, unsaved-changes indicator (•)
• Workspace: save/load all open pictures as a single .slw file

The editor works like classic ZX Spectrum art programs (Art Studio, Artist II) — drawing in an 8×8 cell sets that cell's attribute to the current ink/paper/bright/flash.

Attribute Editor (.53c / .127c / .atr)

Edit 768-byte attribute-only files with full pattern-aware color selection:

• Pattern palette: unique dither-pattern swatches showing actual ink/paper colors through the selected pattern
  • Adapts to current pattern: Checker (~53 colors), Stripes (~53), DD/77 (~127)
  • Sort modes: Hue, RGB, Color (attribute byte); Reverse toggle
  • "Blend colors" mode renders each cell as a solid averaged color instead of a dither
• Cell painting and drawing tools: pixel, line, rectangle, circle, flood fill, recolor, eraser, color picker
• Layers: full layer support with per-cell masks
• Undo/Redo: 32 levels
• Save: normalized attribute bytes (ink ≥ paper) for ChunkyPaint compatibility

ULA+ Support (64-color mode)

Full support for the ULA+ 64-color extension:

• Format detection: files of 6976 bytes (6912 SCR + 64-byte GRB332 palette) auto-detected as ULA+
• Two palette views: 8×8 grid of all 64 colors, or classic 16-color row with CLUT selector (0–3)
• Editing: Ctrl+click any palette color to edit R (0–7) / G (0–7) / B (0–3) with live preview and undo; Shift+click to copy/swap colors between palette slots
• Import: convert PNG/JPG/etc. to ULA+ with optimal palette generation or from a loaded .pal / ULA+ .scr
• Eyedropper: picks color and auto-selects the correct CLUT
• Palette files: save/load 64-byte .pal GRB332 files (12 bundled palettes in palettes/)
• ASM export: sjasmplus-compatible source for Pentagon 128K / ZX Spectrum 48K with I/O palette programming
• Format conversion: SCR ↔ ULA+ (add or strip palette)

ULANext Support (ZX Spectrum Next extended palette)

View and edit SCR files with ULANext extended palettes:

• Format detection: files in the range 6945–7426 bytes auto-detected as ULANext (SCR + ink mask + palette)
• Configurable ink mask: 8 valid masks ($01–$FF) split the attribute byte between ink and paper indices, from 2/128 to 256/1
• Dual palette sizes: 9-bit RGB333 (2-byte entries, same as NXI) and 8-bit RRRGGGBB (1-byte entries), auto-detected by file size
• Round-trip save: preserves ink mask and palette in original format
• Format info: displays mask value, ink/paper color counts, and palette bit depth

Image Import

Import PNG, GIF, JPG, WebP, BMP and convert to any editable format:

• Output formats: SCR, ULA+, IFL, MLT, BMC4, BSC, BSP, 53c/127c (attribute-only), Gigascreen (.img), MGH (mg1/mg2/mg4/mg8), STL, RGB3, NXI (256×192, 320×256, 640×256), SL2 (256×192, 320×256, 640×256), Monochrome, SPECSCII, ZXP (variable dimensions)
• Automatic scaling to the format's native dimensions (256×192, 320×256, 640×256, 384×304 for BSC/BMC4, 8–2048 custom for ZXP, etc.)
• Dithering:
  • Global: Floyd-Steinberg, Jarvis-Judice-Ninke, Stucki, Burkes, Sierra / Sierra Lite / Sierra 2-Row, Serpentine Floyd-Steinberg, Dizzy (adaptive error diffusion), Riemersma (Hilbert curve), Atkinson, Ordered (Bayer 2×2 / 4×4 / 8×8), Blue noise, a-dither (arithmetic), Pattern (clustered dots), Noise, None
  • Strength slider (0-100%) scales how much quantization error is diffused; for ordered / pattern / blue-noise methods, strength > 0 enables a hybrid ordered+diffusion mode
  • Serpentine scanning checkbox alternates row direction during error diffusion to reduce horizontal banding
  • Cell-aware variants (Floyd/Atkinson/Ordered/None) that dither inside each cell using its chosen colors
  • Per-channel dithering for RGB3 (each R/G/B bitplane dithered independently as 1-bit mono)
• Brightness / Contrast / Saturation: manual sliders with auto-detect
• Color space: LAB color matching for perceptually accurate quantization
• Position / Size / Fit / Align: 9-position alignment (Top-Left … Bottom-Right) for Letterbox / Fill-crop / Fit width / Fit height modes; explicit X/Y/W/H controls with optional aspect-ratio lock
• Paper rule (2-color cells): Darker color / Lighter color / First pixel paper
• Palette source: current display palette, generated ULA+ optimal palette, loaded .pal file, or extracted from an existing ULA+ picture; Ctrl+click palette entries to edit, eyedropper on preview picks a color
• Cell-aware conversion: respects 8×8 / 8×4 / 8×2 / 8×1 attribute constraints per format
• BMC4 border: encodes real border colors from the 384×304 source, respecting Spectrum timing constraints
• Gigascreen / MGH: per-cell brute-force search over ~2628 unique attribute-pair quads for up to 4 perceived colors per cell
• Tile to screens: split a large source image into a grid of output-format pictures
  • Auto-calculates grid from crop area and output format dimensions
  • Edge tiles padded with black; yellow dashed overlay on the source canvas
  • Per-tile preview with navigation; tile filenames name_col_row.ext
  • Works for all output formats including Gigascreen and MGH variants
• Live preview: side-by-side original and converted output with grid overlay and x1–x3 zoom

BSC / BSP / BMC4 (border screen) Editor

Edit .bsc (11136-byte), .bsp (variable, with 70-byte header), and .bmc4 (11904-byte) files with full border editing:

• Per-line border colors for top, bottom, and side borders
• Hidden zone indicator: grid shows leftmost/rightmost 16px with red overlay (typically hidden on real hardware)
• Border drawing: click/drag with rectangle, flood fill and brush-sized vertical lines (left = ink, right = paper)
• Barcodes: vertical color patterns for border decoration — 8 slots, capture with Shift+click, stamp by clicking the border, save/load as .slbc
• Layer system preserves per-layer border data
• BSP header: 70-byte header with title/author metadata, 4 variants (screen, screen+border, gigascreen, gigascreen+border), RLE border compression
• ASM export: sjasmplus Pentagon 128K source with exact 224T/line cycle-accurate timing, 71680T/frame, OUT-on-change + NOPs, SAVESNA output

Gigascreen Editor (.img / .mg1 / .mg2 / .mg4 / .mg8 / .hlr / .stl / gigascreen chr$)

Edit two-frame gigascreen formats with live blended preview:

• Virtual color palette: 136 unique blended colors from 16 ZX colors (8 normal + 8 bright)
• 4-color per cell: each ink/paper pair gives 4 paintable blends (Ink+Ink, Ink+Paper, Paper+Ink, Paper+Paper)
  • Left-click a color → L mouse button; right-click → R mouse button
• Attribute cell heights: 8 (standard), 4 (mg4), 2 (mg2), 1 (mg1, with 8×8 outer columns) — editor adapts automatically
• True dual-frame editing: different pixel patterns per frame, layered with dual-frame attribute storage
• Display modes: Average (blended) or Flicker (50 fps alternating frames)
• HLR fill pattern: editable 8-byte mask defining ink/paper regions per cell, with presets (halves, checker, stripes, diagonals) or custom hex input, live 8×8 preview, undoable pattern changes
• All drawing tools, layers, eyedropper and clear work with virtual colors
• Save: preserves the full file format including MGH 256-byte header (mg*), HLR self-contained loader, or STL interleaved attrs
• ASM export: sjasmplus dual-screen banking (banks 5/7), 25 Hz alternation, SAVESNA output

RGB3 Viewer / Editor (.3)

View and edit 18432-byte tricolor RGB files (three monochrome bitmaps shown in sequence):

• Flicker emulation: cycles R, G, B frames at ~16.7 Hz each for perceived full color
• Blended view: palette-aware averaged color from all three bitplanes (works with every bundled palette)
• Dedicated 8-color palette with L/R (left/right button) selection and bitplane tooltips
• ASM export: unrolled LD HL,nn : PUSH HL copy (21T per 2 bytes), tear-free 50 fps display, SAVESNA output

IFL / MLT / Multicolor Viewers and Editors

• IFL (.ifl) — 8×2 multicolor, 9216 bytes; full editor support
  • ASM export uses POP/PUSH stack technique with dual-screen interlace (show one screen, write the other), 448T per 2-line attr row, compact sjasmplus macros, SAVESNA output
• MLT / .mc — 8×1 multicolor, 12288 bytes; full editor support
• BMC4 — 8×4 multicolor with border, 11904 bytes; full editor and image-import support including border quantization

SPECSCII Text Editor

Edit 32×24 character streams using the ZX Spectrum ROM font plus block graphics:

• Character palette: 112 tiles (96 ROM 0x20–0x7F + 16 block graphics 0x80–0x8F) with live theme-aware preview
• Drawing tools: pixel (place char), line, rectangle, circle, flood fill, eraser, text
• Paint modes: Set, Invert (swap ink/paper), Recolor (attributes only) — all tools respect the current mode
• Layer support: OVER (XOR) compositing with per-cell transparency masks, multiple layers
• Attributes: per-cell ink / paper / bright / flash; right-click picks attributes from the screen
• Copy / cut / paste: full clipboard with invert and recolor paste modes, snap-to-grid
• Custom fonts: load any 768-byte .768/.ch8 bitmap font
• Export: save as .specscii (stream format with embedded AT/INK/PAPER/BRIGHT/FLASH/OVER control codes), render to .scr via Transform tab, or export to self-running .tap BASIC program

chr$ Editor

Support for ZX-based .ch$ / .chr$ / .ch- character-array files:

• 7-byte header: "chr$" magic + width/height in cells + bytes-per-cell (9 = mono/attr, 18 = gigascreen)
• Variable dimensions with linear interleaved 8×8 cell layout
• Gigascreen chr$ (18 bytes per cell): two frames per cell with blended rendering
• Full editor: drawing tools, attributes, layers, copy/paste, clear, save

ZX-Paintbrush (.zxp) Editor

Variable-size ZX-Paintbrush text format, 8–2048 pixels per axis (÷8):

• Load / save / drag-drop .zxp text files from disk or ZIP archives
• Auto-detected attribute mode from line count: 8×8 (SCR), 8×4 (IFL-like), 8×2 (IFL), 8×1 (MLT)
• ULA+ palette support (64-byte palette extension)
• New Picture dialog: configurable width / height / palette type (ULA or ULA+), remembered via localStorage
• Image import: PNG/JPG/etc. → ZXP with custom dimensions
• Fractional zoom (×1/8, ×1/4, ×1/2) and viewport-clipped rendering for large images
• Deferred Catmull-Rom stroke smoothing for big pictures at fractional zoom

Sprite Editor

Full-featured floating sprite sheet editor for ZX Spectrum game graphics:

• Multi-tile sprites: N×M cells of 8×8 pixels (up to 8×8 = 64×64 per frame)
• Modes: Monochrome, Attributed (8×8 cells), Multicolour 8×1 / 8×2 / 8×4
• Drawing tools: Draw (D), Erase (E), Flood Fill (F), Line (L), Rectangle (R), Selection (S), Mask (M)
• Right-click = paper: matches main canvas; Fill left=ink, right=paper
• Mask editing: toggleable mask layer with red overlay; per-sprite transparency
• Transforms: Flip H / V, Rotate CW/CCW (square only), Shift 1px any direction, Invert, Clear
• Attributes: unified color palette, left-click ink, right-click paper, bright toggle; attributes toggle for mono view
• Animation: multiple frames per sprite with onion skinning, adjustable playback speed, frame bar with multi-select (Ctrl/Shift), reorder, duplicate, delete
• Attr scroll: shift arrows scroll attributes along with pixels in multicolour modes
• Spriteset list: multi-select, right-click context menu — Merge to animation, Add/Move frames to another sprite, Split frames to sprites, Delete, Clear all
• Grab from screen: drag a rectangle on any loaded picture to extract sprites
  • Modes: Single sprite, Sprite phases, Singles grid, Phases grid
  • Grid by cell size (W×H) or column/row count; row-first or column-first ordering
  • Auto-detects multicolour source formats (IFL, MLT, BMC4, 8×2 btile/wtile)
• Grab from memory: extract sprites from snapshot RAM via the Memory Viewer (same grab modes)
• Load Nirvana tiles: .btile (column-major attrs) and .wtile (row-major attrs) files open as single variable-size 8×2 multicolour images
• Export ASM: sjasmplus DB lines with visual binary comments (█·), labels, SpectraLab version header
• Export BIN: raw binary or Nirvana engine format (.btile / .wtile) for multicolour sprites
• Save / Load: sprite sheets as .sls files; included in project (.slp) and workspace (.slw) save/load
• Use as Brush: stamp current sprite frame onto the main canvas

Font Editor

Standalone page (font_editor.html) for creating and editing ZX Spectrum bitmap fonts. Open via the Font link in the View tab bottom bar.

• Fixed-width fonts: 8×8 bitmap fonts with arbitrary glyph count (1–255), width modes (8/6/4/variable)
• FZX proportional fonts: variable glyph width (1–16px), configurable height (1–16px), per-glyph shift and kern, signed tracking
• UDG support: load, edit, and save UDG blocks (21 characters A–U, char codes 144–164)
• File formats: .768, .ch8, .bin, .SpecCHR, .fnt, .fzx; visual format chooser for 2048-byte files (normal vs interlaced)
• New font dropdown: 96 glyphs, 256 glyphs, 96+UDG, 256+UDG, custom glyph count, new FZX font
• Save format dropdown: choose output format per font type
• Pixel editor: 32× zoom, click/drag to toggle pixels; variable width mode protects width byte (row 0) with optional Hide W checkbox
• Transforms: 22 operations — bold (3), italic (6), shift (4), flip/rotate (5), align (4); applied to single glyph or whole font
• Copy/paste glyphs: Ctrl+C / Ctrl+V with cross-format conversion (fixed ↔ FZX)
• Convert: fixed ↔ FZX with visual bounding box detection and left-aligned bitmap
• Undo/redo: up to 50 levels (Ctrl+Z / Ctrl+Y), covers all modifications including FZX property edits
• Character mapping: map strings to glyph ranges, Cyrillic↔Latin remap, export/import .metrics JSON
• Grid options: pixel gap grid, glyph labels (mapped character under each glyph)
• Whole font editing: pixel changes and transforms apply to all glyphs at once (respects per-glyph variable width)
• Arrow key navigation: navigate glyphs in the grid
• Theme: synced with SpectraLab via localStorage

Snapshot Support (.sna / .z80)

Load ZX Spectrum memory snapshots and extract pictures and sprites:

• SNA: 48K and 128K formats
• Z80: V1, V2, V3 with RLE decompression
• Screen extraction: 48K main screen, 128K normal (bank 5) + shadow (bank 7); empty screens skipped
• Border color set from snapshot header
• ZIP-aware: snapshot files inside .zip archives are detected automatically

Memory Viewer

Floating panel for browsing snapshot RAM as 1-bit graphics:

• Renders any memory bank as green-on-black bitmap (16 bytes per row)
• Bank selector for 128K snapshots (empty banks filtered out)
• Navigation: byte / line / row (8 lines) / sprite / page steps, vertical scrollbar, mouse wheel
• Mouse-driven selection: click to position a red rectangle, drag to resize; W/H inputs update live
• Address label in decimal and hex
• Adjustable sprite size (W 1–8 bytes, H 1–64 rows)
• Preview canvas (2× zoom) shows the selected sprite
• Linear and Char addressing modes (Char = 8×8 tile layout)
• Invert display, per-byte vertical and per-8-row horizontal grid overlays
• Zoom x1–x4, draggable floating panel
• Grab to Sprites: four grab modes (Single, Phases, Singles grid, Phases grid) with cell-size or col/row grid sizing, row-first or column-first ordering

SCA Animation (.sca)

Play and edit ZX Spectrum animation files:

• Type 0 full frames (6912 bytes per frame) and type 1 attribute-only (768 bytes per frame with 8-byte bitmap fill pattern)
• Pattern selector for type 1: File (embedded), Checker, Stripes, DD/77; optional "Blend colors" mode
• Playback: play/pause (Space), previous/next frame (←/→), frame-by-frame scrub with wrap-around
• SCA Editor (Edit tab): trim start/end, per-frame and bulk delay adjustment, manual frame deletion (Ctrl+click or Del/Backspace), duplicate frame detection and optimization, loop-frame removal
• Filmstrip preview with thumbnails and x1/x2/x3 zoom
• Export dropdown: SCA, SCR zip, 53c zip, animated GIF (with per-frame delays), PNG series zip

Display Filters

Collapsible section in the View tab with CRT/retro post-processing effects:

• Scanlines — Gaussian beam profile with brightness-dependent width (modeled after crt-geom/crt-lottes)
• Noise — static film grain with optional animation (~12 fps)
• Composite — chroma blur simulating composite video color bleed (YCbCr horizontal box blur)
• Phosphor Glow — blurred screen-blend overlay
• Vignette — radial edge darkening
• CRT Curvature — barrel distortion
• Pixel Smoothing — bilinear interpolation toggle
• Presets: None, CRT TV, Composite, VHS, Arcade
• Master On bypass checkbox; settings persist to localStorage and workspace files
• Works in both viewer and editor fullscreen modes

Supported Formats

Extension	Size	Description
.scr	6912 bytes	Standard screen (bitmap + attributes) — editable
.scr	6976 bytes	SCR + ULA+ 64-color palette — editable
.scr	6945–7426 bytes	SCR + ULANext palette (ZX Next, up to 256 colors) — editable
.scr	6144 bytes	Monochrome (bitmap only) — editable
.scr	4096 bytes	Monochrome 2/3 screen — editable
.scr	2048 bytes	Monochrome 1/3 screen — editable
.53c / .127c / .atr	768 bytes	Attribute-only with pattern palette — editable
.bsc	11136 bytes	Border screen (SCR + per-line border) — editable
.bmc4	11904 bytes	Border + 8×4 multicolor — editable
.ifl	9216 bytes	8×2 multicolor — editable
.mlt / .mc	12288 bytes	8×1 multicolor — editable
.3	18432 bytes	Tricolor RGB (3 bitmaps), flicker or blended — editable
.img	13824 bytes	Gigascreen (2×SCR), average/flicker modes — editable
.mg1 / .mg2 / .mg4 / .mg8	variable	Multiartist MGH gigascreen with 256-byte header — editable
.hlr	1628 bytes	Gigascreen Lowres with self-contained loader + 8-byte fill pattern — editable
.stl	3072 bytes	Stellar (64×48 multicolor gigascreen) — editable
.bsp	variable	Border screen with 70-byte header (screen/gigascreen ± border) — editable
.zxp	variable	ZX-Paintbrush text format, 8–2048 px per axis (÷8), optional ULA+ — editable
.ch$ / .chr$ / .ch-	variable	chr$ character array, 8×8 cells, optional gigascreen — editable
.btile / .wtile	variable	Nirvana 8×2 multicolour tile sets — editable
.specscii	variable	Text mode with colors (stream + control codes) — editable
.sca	variable	Animation (type 0 full frames, type 1 attribute-only) — editable
.nxi	49664 / 82432 / 81952 bytes	ZX Next Layer 2 (256×192, 320×256, 640×256) + palette — editable
.sl2	49152 / 49280 / 81920 bytes	ZX Next Layer 2 (256×192, 320×256, 640×256), default palette — editable
.sna	49179 / 131103 bytes	48K / 128K ZX Spectrum snapshot — screen extraction
.z80	variable	Z80 snapshot (V1, V2, V3 with RLE) — screen extraction
.pal	64 bytes	ULA+ palette (GRB332)
.slp	variable	Project file (single picture with layers, masks, per-layer attributes, border data)
.slw	variable	Workspace file (all open pictures + global settings + sprite sheet + filters)
.sls	variable	Sprite sheet (sprites with frames, attributes, modes)
.slb	variable	Brush set (loaded as a new tile tab)
.slbc	variable	Barcode set (border color patterns)
.768 / .ch8 / .fnt	768–2048 bytes	ZX Spectrum bitmap font (96/256 glyphs, normal or exploded)
.fzx	variable	FZX proportional font
.metrics	variable	Font character mapping metadata (JSON)
.zip	—	Archive (auto-extract, recursive file detection)

Keyboard Shortcuts

All letter shortcuts work with any keyboard layout (Russian, German, etc.) — based on physical key position.

Viewer

Key	Action
1-5	Set zoom level (x1 to x5, higher via menu)
F	Toggle flash animation
G	Toggle grid overlay
~	Toggle preview panel
F11	Toggle viewer fullscreen
Space	Play/Pause animation (SCA)
Left/Right	Previous/Next frame (SCA)

Screen Editor

Key	Action
P	Pixel tool
L	Line tool
R	Rectangle tool (or Rotate when pasting/custom brush)
O	Circle/ellipse tool
Ctrl	Constrain rect/circle to square/circle (1:1)
Alt	Draw rect/circle from center; eyedropper (pick color from canvas)
G	Airbrush tool
D	Gradient tool
I	Flood fill tool
C	Fill cell tool
A	Recolor tool (attribute only)
E	Eraser tool (transparent on upper layers, paper on background)
K	Color picker tool
T	Text tool
S	Select tool (drag to select, auto-copies)
H	Mirror horizontal (when pasting/custom brush)
V	Mirror vertical (when pasting/custom brush)
N	Invert selection (swap ink ↔ paper)
X	Swap ink/paper colors
B	Toggle Bright
F	Toggle Flash attribute
[ / ]	Decrease/Increase brush size
`	Toggle brush preview mode
Ctrl+Wheel	Zoom toward cursor
Ctrl+C	Copy selection
Ctrl+X	Cut selection
Ctrl+V	Paste (enter paste mode)
Ctrl+Z	Undo
Ctrl+Y / Ctrl+Shift+Z	Redo
Ctrl+S	Save
F11	Toggle fullscreen editor
Tab	Toggle floating palette (in fullscreen)
Escape	Cancel selection/paste, exit fullscreen

Sprite Editor

Key	Action
D	Draw
E	Erase
F	Flood fill
L	Line
R	Rectangle
S	Selection
M	Toggle mask layer
Ctrl+Z / Ctrl+Shift+Z	Undo / Redo

Usage

Open index.html in any modern web browser. No server required — runs entirely client-side. Files can be loaded via the Browse button, dragged and dropped anywhere on the window, or selected from inside ZIP archives.

Resources & References

Tools and documentation that inspired or informed SpectraLab development:

• img2zxscr — PNG to ZX Spectrum converter (Go)
• PNG-to-SCR — Online JavaScript converter
• Image to ZX Spec — Cross-platform converter with dithering
• img2spec — Image Spectrumizer tool
• World of Spectrum — ZX Spectrum documentation and resources
• FZX format — FZX proportional font format specification

License

MIT

The example pictures in the examples/ directory are works of ZX Spectrum pixel art. All rights to these works belong to their respective authors.