Finish the background mask before choosing a colour
Recolouring works best after the surrounding paper has been removed. If the image still includes a grey shadow or white patch, changing RGB colour does not necessarily make that area transparent. Prepare the mask first and compare it with the source so faint strokes, dots, and spaces inside letters remain recognizable.
Use a close view to inspect fine edges and normal document size to judge readability. If a pale paper fringe remains, correct that local area rather than making the entire image darker. Keep an original-colour reference. It lets you tell whether a later colour or opacity choice changes the visual impression without losing track of the original marks.
Choose an explicit ink colour
For a black, blue, or organisation-specific variant, use a defined colour rather than trying to imitate it with brightness and contrast. The developing Paperkiss studio offers original ink, preset colours, and a custom six-digit RGB HEX value. A value such as 1B365D specifies the colour channels; it does not include a transparency percentage.
Enter only the intended RGB value and check the preview before saving. If somebody supplies an eight-digit value, clarify whether it includes opacity rather than dropping characters at random. The current Paperkiss custom-colour field validates six-digit RGB input and keeps opacity as a separate adjustment. A correct value still needs a visual check against the actual document background.
Keep the mask and opacity distinct
Alpha describes how much of a pixel is visible. Fully transparent pixels should remain empty when the ink is recoloured; partially visible edges should retain their soft boundary. Painting a coloured rectangle behind the signature is a background change, not an ink-colour change. Check a shaded page area to distinguish those outcomes.
Paperkiss photo processing applies the chosen ink RGB to the prepared foreground and applies opacity separately to its alpha. This is the implemented pipeline, not a promise that every source photo will need no manual correction. When judging the result, watch the lightest joins: lowering opacity can make a fine stroke hard to see even though its shape was preserved.
Compare original and variant on useful backgrounds
Inspect the same crop with original ink and with the selected colour. Use white to judge ordinary document readability, grey to reveal leftover paper, and dark to inspect bright fringes. Do not choose an ink colour solely because it looks vivid on a checkerboard. The mark must remain readable on the page where it will actually be placed.
If a recoloured stamp loses a pale line, return to the mask rather than compensating with a thicker overall result. If the entire mark looks too faint, check the opacity setting and the original source. Keep any preparation faithful to the existing handwriting or stamp content. A new colour is a presentation choice, not evidence that a signature or stamp is authentic.
Save a separate colour variant and check the export
Name variants by their intended use, such as “Personal signature — navy” and “Personal signature — original”. The implemented library workflow can save a prepared item as a variant, keeping the reference available. This is safer than repeatedly overwriting the only version whenever a different form needs a different ink colour.
Export a transparent PNG, or a WebP accepted by the destination, and reopen it over a coloured background. Confirm that only the ink changed, no opaque rectangle appeared, and the soft edges remain reasonable at the final placement size. Paperkiss is in development; the eventual Windows workflow still needs review on your own files. Keep the master until you have inspected the finished document output as well.
Questions and answers
Is opacity part of a six-digit HEX colour?
No. Six-digit RGB specifies red, green, and blue. In the Paperkiss preparation workflow, opacity is adjusted separately and affects the visibility of the prepared ink.
Will changing the colour remove a paper shadow?
No. Deal with the paper and its shadow in the background mask first. Recolouring a poorly prepared image can preserve an unwanted patch.
Should I replace the original library item?
Keep an original-colour reference and save a named variant when you need another colour. That makes comparison and future exports easier.