Authentic GBC for ReShade

A ReShade port of fishku's "Authentic GBC" shader. It recreates the look of a Game Boy Color LCD by rendering the individual RGB subpixels — including the characteristic little "notch" (dog-ear) on each one — using analytical pixel coverage for clean, sharp anti-aliasing.

The original is a libretro slang shader; this port packages it as a single self-contained .fx so it can be used in any game or emulator that supports ReShade, on any rendering backend.

The screenshots show Mina the Hollower © Yacht Club Games, used under their video/content policy to demonstrate the shader.

Features

• Authentic GBC subpixel rendering with the signature notched subpixels.
• Adjustable brightness, anti-banding smoothing, and optional subpixel offset.
• Selectable subpixel layout (RGB / BGR, horizontal or vertical).
• Two quality modes: Accurate (Gaussian-smoothed coverage) and Fast (cheaper box-filter approximation).
• Works on any source resolution, not just 160×144 — usable for NES, SNES, Genesis, GBA and more.
• Two display modes: Fill screen for fullscreen content and Centered for a console image pillarboxed on a wider display, with untouched borders.

Requirements

• A game or emulator with ReShade installed.

Installation

1. Install ReShade into your game/emulator, choosing the rendering API it uses (Direct3D, OpenGL, or Vulkan).
2. Copy AuthenticGBC.fx into your reshade-shaders\Shaders\ folder.
3. Launch the game, open the ReShade overlay (default Home key), and enable Authentic GBC in the technique list.

Settings

All controls appear under the Authentic GBC category in the ReShade overlay and can be changed live.

Setting	Default	Description
Source resolution (px)	160 x 144	Native pixel resolution of the source content; the LCD grid is built from this. Set it to match what you're applying the shader to (see the per-system table below).
Content scaling	Fill screen	Fill screen: the source is assumed to cover the whole screen. Centered: an aspect-correct image sits in the middle with untouched borders.
Display aspect	Square pixels	Centered only. Square pixels (Game Boy / GBC / GBA), 4:3 (CRT) (NES / SNES / Genesis), or Custom.
Custom aspect (w / h)	1.3333	Centered only. Used when Display aspect is Custom (e.g. 1.3333 = 4:3).
Snap to integer scale	On	Centered only. Locks the vertical scale to whole pixels; match an emulator using integer scaling. Turn off if your emulator scales to fit exactly.
Center nudge (px)	0, 0	Centered only. Fine offset if the image isn't perfectly centered.
Add brightness	0.60	Brightens the image by enlarging each subpixel.
Anti-banding smoothing	0.30	Softens subpixel edges to reduce banding.
Enable subpixel rendering	Off	Adds a horizontal/vertical RGB offset within each pixel.
Subpixel layout	RGB	Subpixel arrangement: RGB, RGB vertical, BGR, or BGR vertical.
Quality	Accurate	Accurate = Gaussian coverage (matches the original two-pass preset). Fast = box-filter approximation (lighter; gamma 2.0).

Display modes

ReShade runs on the final rendered frame and has no knowledge of an emulator's native framebuffer or the games internal resolution, so you have to tell the shader where the image is via these two modes.

Fill screen assumes the source image covers the entire backbuffer. Use it for fullscreen pixel-art games (Shovel Knight, Mina the Hollower, Stardew Valley) or an emulator stretched to fill the screen. Set Source resolution to the game's internal pixel resolution so the grid lands on real pixels. For best results the content should be nearest-neighbour scaled.

Centered (pillarbox) places an aspect-correct image in the middle of the screen and leaves the borders untouched — so black bars stay black instead of being filled with subpixels. Use it when emulating a console that doesn't fill a widescreen display. Set Source resolution and Display aspect for your system, keep Snap to integer scale on, and set your emulator to integer / pixel-perfect scaling so the shader's rectangle and the emulator's image coincide. If your emulator stretches to fit instead, turn integer snap off. Small positioning differences can be corrected with Center nudge.

Alignment note: in Centered mode the shader samples the source from where it computes the rectangle to be (a centred, aspect-correct, optionally integer-scaled rect). This lines up automatically when the emulator also integer-scales and centers. If the emulator draws at a different fixed scale, the two rectangles won't coincide — set the emulator to integer scaling so they match.

Per-system reference (Centered mode)

System	Source resolution	Display aspect
Game Boy / Game Boy Color	160 x 144	Square pixels
Game Boy Advance	240 x 160	Square pixels
NES	256 x 240	4:3 (CRT)
SNES	256 x 224	4:3 (CRT)
Genesis / Mega Drive	320 x 224	4:3 (CRT)

Credits

• Original shader: "Authentic GBC" (v2.2) by fishku (GitHub: @fishcu), released into the public domain under CC0. Part of the libretro slang-shaders project (handheld/shaders/authentic_gbc/).
• Pixel-coverage helper (coverage.inc): also by fishku, from the same project (misc/shaders/coverage/).
• ReShade (.fx) port: PointSampler, using Claude Opus 4.8.

If you enjoy the shader, the credit really belongs to fishku — please point people to the original project.

License

The original shader is dedicated to the public domain under CC0 1.0. In keeping with the original, this port is also released under CC0 1.0 — do whatever you like with it. See the LICENSE file for the full text.