What are semi-transparent pixels?
They are pixels that are neither fully clear nor fully solid. In an 8-bit PNG each pixel has an alpha value from 0 (clear) to 255 (solid), and anything from 1 to 254 is semi-transparent. The heatmap above colours every one of them, from blue for barely visible to magenta for nearly solid.
They come from ordinary drawing and export, not from mistakes:
- Anti-aliased edges. Every smooth edge of text, lines and shapes is a row of semi-transparent pixels.
- Soft brushes, blur and feathered selections. Airbrush strokes and blurred edges fade through every alpha value.
- Drop shadows and glows. These are nearly all semi-transparent by design.
- Layers or brushes below 100% opacity. A layer at 60% opacity flattens to pixels at about alpha 153.
To show how common they are, we made three test files with ImageMagick 7.1.1 on 2026-10-16 and counted their pixels:
| Test file | Pixels | Semi-transparent | Share that prints |
|---|---|---|---|
| Black text, no effects | 680×235 | 2,916 | 5.58% |
| Shape with a drop shadow | 1272×972 | 141,408 | 22.83% |
| Circle, blurred 6 px edge | 300×200 | 17,468 | 58.54% |
Even the plain text, with no effects at all, has thousands.
Why do semi-transparent pixels print badly on DTF?
Because there is no semi-transparent ink. A DTF, DTG or sublimation printer can only put ink down or leave the spot empty, so its software has to decide for each semi-transparent pixel. The print company Inkthreadable puts it plainly: the printer will “either lay down ink, or not lay down ink, and the results are usually unpredictable”.
What print shops say they see, in their own help pages (read on 2026-10-16):
- Transfer Superstars, a DTF transfer supplier, writes that glows, shadows, feathered edges and soft blurs “don’t translate well to DTF” and that the semi-transparent pixels “either drop out or print muddy”. It asks for hard-edged, fully opaque shadows.
- Mayzing’s help centre warns that transparent fades can show white halos or outlines where the white underbase shows through, and asks for every layer to be at 100% opacity before export, with a transparent background but fully opaque edges.
How much a given printer is affected depends on its software and white ink settings, so ask your print shop what it wants. This tool lets you see exactly what is in the file before you send it.
Which fix should I pick?
Pick the cut-off for most artwork, make solid when nothing may disappear, and remove faint when you only want to clean up stray haze. Fully clear and fully solid pixels never change. The table shows what each fix does to the rest, by their alpha before the fix:
| Fix | Below the cut-off | Cut-off to 254 | Left semi-transparent |
|---|---|---|---|
| Cut-off | Clear | Solid | None |
| Make solid | Solid | Solid | None |
| Remove faint | Clear | Unchanged | Those from the cut-off up |
- Cut-off keeps shapes the size you drew them, give or take half a pixel at the edge. It works like GIMP’s Threshold Alpha.
- Make solid is right for clean artwork where every visible pixel belongs to the design. Soft shadows, glows and faint brush texture turn into solid shapes, so check the preview first.
- Remove faint deletes near-invisible haze (stray marks from a soft eraser, the outer edge of a glow) and leaves the rest alone. It does not make a file free of semi-transparency.
The side panel shows how many pixels each choice clears, makes solid and leaves, for the file you are looking at.
What does the tool keep and what does it change?
It changes the alpha of the semi-transparent pixels and nothing else that affects how the image prints.
| Part of the PNG | After the fix |
|---|---|
| Width and height in pixels | Unchanged |
| Colour of every pixel | Unchanged (only alpha changes) |
| Fully clear and fully solid pixels | Unchanged |
| Resolution (dpi, the pHYs chunk) | Copied byte for byte |
| Colour profile (iCCP, sRGB, gAMA, cHRM, cICP chunks) | Copied byte for byte |
| Bit depth | 8 bits per channel; 16-bit files are rounded to 8 |
| Palette PNGs | Saved as full-colour RGBA |
| Text and EXIF metadata | Not copied |
| Animated PNG | Only the main image is saved |
The chunk names come from the PNG specification. The file is read by the tool’s own PNG reader rather than through a browser canvas, because a canvas stores colour premultiplied by alpha and would round the colour of faint pixels before they are made solid.
What doesn’t this tool do?
It only changes alpha, so anything else stays as you made it:
- No halftones. Fades become solid or clear, not dots. If a soft shadow matters to the design, convert it to a halftone in your editor instead.
- No background removal. It only touches pixels that are already partly transparent. A white background stays white.
- No resizing or dpi changes. Check the print size with check DPI and set it with change DPI.
- PNG only. JPG has no transparency at all. Export WebP, TIFF or PSD artwork as PNG first; for a Procreate file, Procreate to PNG does that in the browser.
Can I do it in GIMP instead?
Yes, for the cut-off fix. Select the layer and choose Layer > Transparency > Threshold Alpha, then set the value. It works on one layer at a time, and it does nothing if the layer has no alpha channel or its alpha is locked, according to the GIMP manual. This page is for when you want to see and count the pixels first, fix a batch, or don’t have an editor at hand.