Remove known margins and gaps from a sprite sheet

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In sprite-sheet padding, keep 6×4 content, declare all margins 2 and gaps 4, then request padding 0/extrusion 0. The 20×16 padded control becomes 12×8 packed artwork.

Expected result:

Four unchanged decoded content rectangles packed into two columns and two rows, without the declared outside border or gaps.

What you need

First create the transparent-gutter example and keep its actual PNG download. The recorded actual 20×16 intermediate is also available. Do not substitute a generated reference when checking an actual add→download→reupload→remove chain.

Download the source cells and reference round-trip

Tested with: Actual production add/download/reupload/remove chain in local Cloudflare/workerd, desktop Chrome 154/macOS; independent Pillow 12.3.0 decoded-plane checks. Node 24.22.0 source references are separate.

1. Declare the padded input correctly

Choose the actual 20×16 padded PNG. Enter cell width 6, cell height 4, left/top/right/bottom margins 2, horizontal gap 4 and vertical gap 4. Choose padding 0 and extrusion 0, then select Create padded PNG.

The input content origins are (2,2), (12,2), (2,10), (12,10). The gap is 4 because adjacent cells each contribute a 2px gutter. Keep content size 6×4; a 10×8 allocated cell includes padding.

2. Keep and inspect the packed result

Actual twelve by eight sheet after removing the known margins and gaps — Actual 12×8 removal output, made from the actual downloaded padding result.

Output cells begin at (0,0), (6,0), (0,4), (6,4). The actual manifest maps each input crop to its new content rectangle. Independent checks matched every output pixel against the corresponding decoded intermediate.

3. Distinguish recovered content from lost gutters

The original 21×16 source contained diagnostic magenta borders and gaps. Padding discarded those pixels; the packed 12×8 result cannot reconstruct them. The round trip preserves the selected content in the observed decoded basis, not the complete original sheet or its encoded PNG bytes.

Hidden RGB and some partial-alpha colors can change when the browser decodes or exports PNGs. Keep source files separately and compare alpha, opaque pixels and decoded visible composition honestly.

4. Do not guess unknown gaps

A plain 12×8 input with zero margins, gaps, padding and extrusion keeps its geometry; identical PNG compression is not promised. A complete but wrong grid can crop artwork while remaining numerically valid. Inspect the first, last and internal cells.

Negative gaps, overlapping/incomplete geometry and invalid extrusion fail. The tool requires one static PNG and the complete grid, at most 32 cells. It does not discover irregular regions or infer old margins.

5. Reproduce the separate software round-trip

In the extracted padding-trim-workflows folder, run the 26 Node fixture cases, generation and readonly check:

node --test fixture.test.mjs
node generate.mjs
node generate.mjs --check

These references do not select, download or reupload an image through the browser tool.