Match a Stamp & Build a Gauge

Overview

What the tools do

Printed color guides and expert judgment have long been the standard for distinguishing stamp shades — carmine from rose carmine, lake from vermilion. This suite extends that practice to your own scanner by letting you build a calibrated color reference from your own gauge cards, then match your stamps against it with perceptual color science (CIEDE2000 ΔE).

Before you begin

Browser & setup

This tool is designed for use on a computer, not a phone.

Browser

Google Chrome or Microsoft Edge on a computer: everything works.
Firefox and Safari: everything works except the optional Workspace Folder. These browsers don't let a web page keep access to a folder on your computer, so Set Workspace Folder is disabled there ("Workspace folders require Chrome or Edge"). Build a Gauge then saves each gauge as a ZIP download; unzip it and load the folder in Match a Stamp with Choose Folder as usual.
Safari Private Browsing: gauges you load are not kept for your next visit; load the gauge folder again each time.

Files

Scan images in PNG, JPEG, BMP, TIFF, or WebP. Higher resolution scans give more accurate color readings.

Account

An AI Stamp ID account is required: sign in to use Match a Stamp and Build a Gauge. Your scans are still processed in your browser and are not uploaded; the account is only used to sign in and, for From My Collection, to load stamps you have already scanned in AI Stamp ID.

Workspace

Optional. Set a local folder once and the app will automatically organise your gauges, templates, and extractions inside it (Chrome/Edge only).

Match a Stamp with the built-in palette

The fastest way to get started. Use the 364 built-in computer colors to identify a stamp's approximate shade before you've built a custom gauge.

1. 1
   Open Match a Stamp

   Navigate to Match a Stamp from the top navigation bar.

2. 2
   Load your stamp image

   Click Choose Image and select a scan of your stamp. The image appears in the preview canvas on the right.

   Or click From My Collection to use a stamp you've already scanned in AI Stamp ID. Search or page through your stamps and click one to load it. Original photo is selected by default because it keeps the truest colors; choose Cropped stamp if you only want the stamp without its background.

3. 3
   Select a palette

   Computer RGB Colors* is selected by default (364 built-in colors). Leave it selected. Click Apply Options to run the match.

   The app automatically identifies the dominant ink color in your stamp and finds the closest palette colors.

4. 4
   Sample a specific color (optional)

   Hover over the canvas — a small box (default 5×5 pixels) previews the average color under your cursor. Click to lock that sample point. Adjust the Sample box slider to average over a larger or smaller area.

   Use this to focus on the stamp's ink rather than paper or cancellation marks.

5. 5
   Read the match results

   The Color Inspector panel shows HEX, RGB, and HSL values. The match panel shows the best-matching color name and its ΔE00 distance. A colored block overlays your stamp — drag it with the mouse, or move it with the X position and Y Position sliders.

6. 6
   Browse ranked matches

   Click Next and Previous to step through all palette colors sorted by closeness to your sample.

7. 7
   Save your result

   Click Save Result (Download) to download a JPEG of your stamp image with the matched color block overlaid.

Understanding ΔE00

ΔE00 (Delta E 2000) is a perceptual color distance — how different two colors look to the human eye, not just in raw RGB numbers.

Extracting your color gauge card

Scan your printed color guide (Stanley Gibbons, Wonder Color, or any gauge card) and extract each swatch's color to build a named palette matched to your equipment.

1. 1
   Open Build a Gauge

   Navigate to Build a Gauge from the top navigation bar.

2. 2
   Load your gauge image(s)

   Click Load Images. You can load a single card or multiple cards — the app processes them all with the same grid template. Use Previous / Next to move between images in the queue.

3. 3
   Set the grid dimensions

   Enter the number of Rows and Cols that match the layout of swatches on your gauge card, then click Update Grid. A cyan grid appears over the full image.

4. 4
   Fine-tune the grid cells

   Click a cell to select it (it turns yellow). Drag the edges or corners to resize it to align with the printed swatch boundaries.

   Delete unwanted cells by selecting and pressing Delete, or by double-clicking. Use Undo Delete or Ctrl Z to restore.

5. 5
   Colors are read automatically

   You don't pick a spot to sample. Each cell's color is its main color area: the app leaves out white paper, punched holes and printed swatch names on its own, so it works the same on cards whose swatches differ in size and layout. If a cell takes in something it shouldn't, such as part of the next swatch or a large printed label, drag its edges to leave it out. Graduated tint strips have no single color; delete those cells rather than relying on them.

6. 6
   Save a template (optional)

   Enter a gauge name and click Save Template to reuse the grid layout for future batches of the same card.

7. 7
   Extract the colors

   Enter a Gauge Name (e.g. SG_Card_1) and click Extract Colors. If a Workspace Folder is set, files are saved to extracted-gauges/<gauge-name>/. Otherwise a ZIP download begins containing the palette CSV and individual swatch PNG crops.

Matching your stamp against the gauge

1. 1
   Open Match a Stamp

   Navigate to Match a Stamp.

2. 2
   Load your stamp image

   Click Choose Image and select your stamp scan, or load it with From My Collection. For gauge matching, use a stamp scanned on the same scanner, with the same settings, as your gauge card. A phone photo from your collection won't compare fairly against a scanned gauge.

3. 3
   Select a gauge slot

   Choose one of the three Color gauge radio buttons (1, 2, or 3). The Choose Folder button appears.

4. 4
   Load your extracted gauge folder

   Click Choose Folder and select the folder containing your extracted gauge CSV and swatch PNGs. The gauge is saved in your browser and reloads automatically on your next visit.

5. 5
   Apply and match

   Click Apply Options. The stamp is matched against your gauge palette and results are ranked by ΔE00.

6. 6
   Browse with swatch overlays

   When your extracted gauge folder includes swatch PNG images, the matched swatch photo overlays your stamp in the preview — giving a direct side-by-side visual comparison. Use Next / Previous to step through ranked matches. Drag the overlay with the mouse, or adjust its position with the X and Y sliders.

7. 7
   Save your result

   Click Save Result (Download) to download the composite image for your records.

Power feature

Workspace Folder

A Workspace is a local folder on your computer that the app uses as an organised home for all your color tool files. Setting one up is optional, but recommended for anyone working with multiple gauges.

How to set a workspace

On either the Match a Stamp or Build a Gauge page, click Set Workspace Folder and choose any folder on your computer. The app creates three sub-folders inside it automatically:

• input-gauges/ — place raw gauge card images here for easy access in the Extractor
• extracted-gauges/ — extractions are saved here automatically, one sub-folder per gauge name
• templates/ — grid templates saved from the Extractor are stored here and can be reloaded by name

For best results

Scanner color calibration

Out-of-the-box scanners apply their own color interpretations — oversaturation, color casts, or crushed shadows — before the file ever reaches your screen. Calibrating your scanner creates a custom ICC profile that anchors its output to known, measurable Lab values. For stamp shade work, where a match and a near-miss can differ by a ΔE of 1–2, a calibrated scanner is the single biggest accuracy improvement you can make.

Consider calibrating your scanner and creating an ICC profile before using this program for the best color matching. Learn about scanner calibration at SilverFast, VueScan, and Wolf Faust.

Best practices

Tips for accurate results

• Scan your gauge card and your stamps on the same scanner, with identical resolution, brightness, and color mode settings. This is the single most important factor for accurate matching.
• Use a flat-bed scanner rather than a phone camera where possible — consistent, even lighting eliminates shadows that skew color readings.
• When extracting, fit each grid cell to its printed swatch. The color is read from the cell's main color area, so a cell that spills into a neighbouring swatch can pick up the wrong color.
• Match a Stamp finds the stamp's main ink color automatically. If that isn't the color you want, for example on a stamp printed in two or more colors, or when a heavy cancellation or toned paper skews the reading, move over the stamp and click to lock a sample on solid ink of the color you want to identify. Set the Sample box size before you click.
• A ΔE00 below 3.0 against your own scanned gauge is a strong match. Results above 6–8 suggest the shade is between gauge entries or the scanner settings differ.
• Keep gauge names short and descriptive: SG_Card_1, Wonder_No3. The name appears in CSV column headers and swatch filenames.
• Process all cards from the same gauge in one extraction session with the same template. This ensures RGB values are directly comparable across cards.
• Your extracted gauges are saved in your browser's local storage. If you switch computers or browsers, re-load the gauge folder to restore them.

Know your reference

Gauge limitations

A match can only be as good as the colors in the palette you match against. A large ΔE00 usually means the right color isn't in that palette, not that the extraction went wrong.

• Printed gauges hold a limited set of colors. Cards like the Wonder Color Gauge and the Stanley Gibbons key are made for printing inks, so their solid swatches are mostly deep, saturated shades. Pale backgrounds and tinted papers often have no close entry: a ΔE00 above about 10 against a gauge means "nothing on this gauge is near", not a bad reading.
• The 364 built-in colors cover more ground. They include pastels and light tints, so they can give a lower ΔE00 on pale colors. Their names are computer color names (Pastel Green, Light Blue), not philatelic shade names, so use them to describe a color, and your gauge to name a shade.
• Graduated tint strips give one color. Strips that fade from light to dark (the Wonder Gauge's tints) are read as their main color area, which is usually the darker part of the fade. Their pale end does not make it into the gauge. Delete tint cells you don't want in the palette. To sample several colors along a tint strip, use more boxes than the card has swatches: raise Rows or Cols until the strip is covered by one box per tint, delete the boxes you don't want, and drag the edges of the rest to fit their swatches. Each box on the strip becomes its own color, in the same gauge. Or crop your scan to just the strip, load the crop and set the grid to one box per tint (for example 1 column and 5 rows for a strip of 5 tints running top to bottom), then extract it under its own gauge name and load it in a free gauge slot in Match a Stamp.
• Match the design color the gauge was made for. Gauges are meant for the printed ink of the design (frame, portrait, value), not for paper or background tints. Lock a sample on solid ink for the most meaningful result.
• Gauge colors are named by position. An extracted gauge names each color by image, row and column (for example WG_5_r7_c3). You can give colors their printed names (for example Carmine) by renaming them in the gauge's folder under extracted-gauges: change the name in the first column of the CSV named after the gauge (not extract_all_colors.csv) and rename the matching swatch image (.png) to exactly the same name, then load the gauge folder in Match a Stamp again. Keep each name unique within the gauge. Extracting the gauge again brings back the position names.
• Your scan is part of the gauge. Extracted colors reflect your scanner, its settings and the card's age and fading. Scan the gauge and your stamps the same way; a gauge scanned on one device is a weaker reference for stamps scanned on another.

Troubleshooting

Common issues

"JSZip failed to load"

Check your internet connection — the JSZip library loads from the page on first use. Reload the Extractor page and try again.

Workspace button missing or greyed

You're likely on Firefox or Safari. Use Chrome or Edge to access the Workspace Folder feature.

Match results seem wrong

Try clicking on the stamp's ink area to lock a sample point before matching. The auto-detected dominant color may be picking up paper tone or a cancellation mark.

Gauge loads but no swatch images appear

Ensure the folder you loaded contains both the palette CSV and the PNG swatch files in the same directory. The swatch image filenames must match the names in the CSV.

High ΔE00 against my own gauge

Check that the gauge card scan and stamp scan used the same scanner settings. Even a small change in brightness or color mode will shift the reference.

Grid cells don't align with my swatches

After clicking Update Grid, drag the edge or corner of individual cells to resize them. Cells don't have to be uniform — each one stores its own fractional position.