Print Preflight Checker for Doujinshi & Comics

What this tool does

Load a PNG or JPEG to inspect pixel dimensions, effective resolution and file metadata. Optional monochrome checks inspect tone levels, recurring dot patterns and fine strokes. The experimental channel model is separate reference information and is never an ink-compliance or color-gamut check. Multiple files can be examined in a page table and exported as reports.

• CSP manual: Exporting files (Japanese) — Official reference; checked 2026-09-06
• CSP official: Creating CMYK data (Japanese) — Official reference; checked 2026-09-06

Who it is for

It is aimed at people sending doujinshi, indie comics and zines to a commercial printer, and at anyone printing posters or merch from digital artwork. Print shops publish a specification sheet with a required dpi, a bleed size and an ink limit, and the usual failure is not knowing whether the export meets it until the printed copy is wrong.

• A last check, right before submission, that the export matches the printer specification
• Inspecting dark areas visually, while checking actual CMYK plates in the exporting application
• Covers where text, logos or a QR code may sit too close to the trim line, and full-bleed pages where the artwork has to run past the trim edge
• Monochrome pages, to catch tones left un-reduced, strokes too thin to print, and screens too fine for the resolution

How to use it

1. Pick the closest use preset: doujinshi color cover or interior, monochrome comic interior, merch and posters, or a custom print shop spec.
2. Adjust the trim size, bleed, safe margin, required resolution and total ink limit to match your printer specification sheet.
3. Turn on the monochrome artwork check if you are sending monochrome or greyscale pages. The monochrome comic interior preset has it on already.
4. Load the artwork by dragging and dropping it or picking it from the file dialog. To check a whole interior, select every page at once.
5. Start with Requirements to check in the results panel and compare the measurements with your printer’s specification. With several pages loaded, select a row to inspect that page.
6. Inspect the measured image warnings and export a report if needed. Experimental channel heatmaps show only the selected model, not a prediction of where print will fail.

What each setting means

Use preset

Five starting points. Choosing one switches the trim size, required resolution, bleed and total ink limit together.

Bleed

The extra artwork beyond the trim size, so a slight drift in the cutting does not leave a white strip of paper at the edge. Three millimetres is the usual request.

Safe margin

The band just inside the trim line where you should avoid putting anything important. A lot of high-contrast detail there raises a warning.

Required resolution

The dpi your printer asks for: commonly 350 dpi for colour work, 600 dpi for monochrome comic pages. With the trim size and bleed it gives the pixel dimensions your export has to reach.

Total ink limit (TAC)

Actual TAC is the sum of the document’s CMYK plates. Here the reference limit only colors and summarizes the experimental model; it does not test drying, set-off or compliance with an ink limit. Inspect the actual plates in an ICC-aware application.

Experimental model

Experimental model A–E changes the channel arithmetic. These are not paper simulations or ICC profiles and cannot be chosen as substitutes for the printer’s profile.

Monochrome artwork check

Reads the tone levels, looks for a periodic halftone screen and measures the thinnest stroke, on the original-size pixels rather than the downscaled copy. It costs about a second per page, so it is off for colour artwork.

Reading the results

• The result indicates whether an implemented check found an issue, requires review, or found none. It does not approve the file for print. Start with the listed issues and compare them with the actual specification.
• Background information records assumptions such as RGB interpretation and white compositing. It is not evidence of print suitability. A page with no detected issue still needs all checks this tool does not implement.
• Max TAC, average TAC and channel differences are outputs of an idealized RGB model. They are not the file’s actual plates, actual ink coverage or a color-proof prediction.
• Dark-area ink combinations shown here belong to the selected model. Verify real rich black, thin-line separation and total ink limits in the exported CMYK document with the intended profile.
• Under the monochrome check, "tone levels" is two-tone, almost two-tone (anti-aliased), greyscale, or chromatic pixels mixed in. Midtone that only hugs an edge is read as anti-aliasing; midtone spread across an area is greyscale.
• "Periodic screen" is an estimate, not a verdict: read the line count and angle as something to check against the tone settings you used in Clip Studio Paint. "Thinnest stroke" is measured with screened areas left out, and anything under 0.1 mm at the output size raises a warning.
• Anything the file header does not state is shown as unknown, not filled in with a default. The page table lists the verdict, estimated dpi, max TAC and critical count per page, and the Markdown export is a checklist you can hand to a print shop as it is.

Fixing them in Clip Studio Paint

When the resolution falls short

Enlarging an exported file with Edit menu > Change Image Resolution will not help: Super resolution (Smart Smoothing) only smooths the roughness of enlargement, it does not add detail that was never drawn. Go back to the source .clip, start it with File > New under the Printing of fanzine (EX only) work purpose, and set Resolution to 600 or 1200 dpi when the Basic expression color is monochrome, or 350 or 600 dpi when it is color or gray.

When the bleed falls short

Use Edit menu > Change Canvas Size, keep the reference point centered, and extend the width and height so the artwork reaches further out on every side. If you can go back to the source file, start a new canvas with File > New, choose Printing of fanzine (EX only), set Trim size to the finished dimensions, and pick a Bleed width of 5 mm or 3 mm so both lines are on the canvas from the start.

When two-tone artwork comes back anti-aliased

Turn off Anti-aliasing in the Tool property palette for your pens and fill tools and redraw the affected strokes, or set Expression color to Monochrome in the export settings and pick a threshold there. Grey you want as a tone should be turned into a halftone screen first, with Tone switched on in the Layer property palette.

When you check and export in CMYK

Open View menu > Color profile > Preview Settings, choose the canvas and display profiles, then turn on Color profile > Preview to soft-proof CMYK on your RGB screen. To export, use File menu > Export a merged image, pick the format your printer requires (psd, for instance), set Expression color to CMYK, turn on Embed ICC profile, and set Output size by resolution to the required dpi.

How the numbers are calculated

The optional CMYK channels use sRGB arithmetic and an idealized black-generation model. Pure channel endpoints remain unchanged, so this cannot detect out-of-gamut primaries. The pixel-to-size calculation is independent: dimensions divided by trim plus bleed give effective dpi. File headers provide embedded dpi, color mode and ICC presence. White or transparent edges are a visual review cue; intentional white artwork is not automatically missing bleed.

How the monochrome check works

This check reads the original-size pixels instead of the downscaled copy, because the interpolation of downscaling invents grey a 1-bit page never had, erases one-pixel strokes and destroys the period of a screen. It runs in three stages - tone levels, then the periodic screen, then the stroke width with screened areas taken out - so a halftone dot is never counted as a hairline. Tone levels come from the luminance histogram plus a test for whether midtone pixels touch both near-black and near-white, which is what separates anti-aliasing from a page never reduced to two tones. The screen comes from the two-dimensional autocorrelation of small two-tone tiles, keeping only the places where a neighbouring tile agrees on both period and angle, with no FFT involved. Stroke width is the shortest horizontal or vertical run through each inked pixel.

Accuracy, and what is out of scope

This tool is in beta. It performs an approximate CMYK estimate inside your browser: it reads whether an ICC profile is embedded, but never applies one and never runs a colour-managed conversion. Strict ICC conversion, PDF/X validation, .clip parsing and automatic correction are out of scope. Treat the output as a way to catch obvious problems early, not as a colour proof.

• The colour you get depends on the press, the paper and the ink at your print shop, so check your CMYK export settings in Clip Studio Paint against the ICC profile your printer specifies. The separation model can express every RGB value, so it never reports a colour as out of gamut.
• A CMYK JPEG is converted to RGB by the browser before the analysis, so the separation stored in the file is gone. Judge the plates in the software that wrote it.
• The bleed and safe area checks assume the outer edge of the image is the bleed area, so a file exported at exactly the trim size gives the bleed warning nothing to measure.
• The line count and angle of a screen are estimates. Small tiles are sampled rather than the whole page, so a tone over a small area can be missed, and evenly spaced hatching reads as a screen too. Width is measured from horizontal and vertical runs, so a thick 45-degree stroke reads about root-two too thick: it errs towards missing a hairline, not inventing one.

How your images are handled

Loading and analysis both happen inside your browser. Your artwork is never uploaded, and neither are the reports you export. Only the print settings are kept, in browser local storage, so the tool remembers your printer specification next time. The images are not stored and disappear when you close the page.