Check PNG interlacing in ManYue: Adam7 passes cover pixels rather than add pages

A PNG interlace method is not a comic chapter count. Make an original eight-by-eight pixel grid, inspect the IHDR interlace field externally and trace Adam7 coverage by coordinates. In ManYue read the complete page rather than seek seven separate pages. No pass display is required, and one visible loading sequence cannot establish progressive behaviour in every decoder.

Make a grid with identifiable coordinates

Create an eight-pixel-wide, eight-pixel-high sample externally, with original colours distinguishing positions, and retain an enlarged coordinate diagram. Set the upper-left to zero/zero, x rightward and y downward, each ranging zero through seven. Name original and enlargement separately so the latter’s dimensions do not enter the calculation. Use a static PNG without animation-control chunks: Adam7 passes differ from APNG frames and multiple images inside a CBZ.

Confirm the interlace flag externally

Inspect a copy’s IHDR with a trusted tool and record dimensions, bit depth, colour type and interlace method. One means Adam7; zero means no interlacing. Slow downloading or gradual appearance does not establish the flag. If the exporter creates only method zero, record it and keep pass tracing a paper exercise. Readability does not prove field inspection occurred. Unknown tool output stays unknown, without modifying a library merely to manufacture this sample.

List the first four coordinate passes

For the eight-by-eight image, pass one starts at zero/zero with strides eight/eight, yielding one point. Pass two starts four/zero with the same strides, also one. Pass three starts zero/four with strides four/eight, yielding two. Pass four starts two/zero with strides four/four, yielding four. Mark passes separately and count only coordinates zero through seven. Stride is neither magnification nor scrolling distance. On smaller images some passes may be empty; a pass number does not justify inventing pixels.

Complete three passes and verify coverage

Pass five starts zero/two with strides two/four, yielding eight points; pass six starts one/zero with two/two, yielding sixteen; pass seven starts zero/one with one/two, yielding thirty-two. Counts one, one, two, four, eight, sixteen and thirty-two total sixty-four, matching eight times eight. Also check unique coordinates and no gaps: equal totals alone could hide offsetting duplicates and omissions. Points are positions of original pixels, not seven source pages at different resolutions.

Make a same-size noninterlaced control

Export method-zero B from the same lossless source, matching dimensions, samples and transparency, with A confirmed as method one. File sizes may differ; do not prescribe which is smaller or by how much faster. If pixels changed, correct export conditions before attributing a difference to interlacing rather than palette quantisation. Preserve reports and source separately. Similar import thumbnails are appearance observations, not replacements for field evidence or a pixel-by-pixel comparison.

Inspect the complete page in ManYue

Place the samples in your own test image collection or supported comic copy and open through an existing local path with matched zoom and background. Magnification may be necessary; smoothed interpolation does not create original pixels. Record page count, markers and complete image. Two archive entries mean two images, not seven pages generated by A. No visible progressive display is a valid observation: a decoder may wait for complete data, so absence of that effect does not prove the flag became zero.

Check confusion between passes and resolution

If the record says seven eight-by-eight images, revisit disjoint coordinate coverage. If the first one-point pass allegedly gives a one-pixel source, restore the full IHDR dimensions. Blurriness calls for checking zoom and sample size before alleging missing pages. Missing cells require checking starts and strides, not editing the total to sixty-four. Share the original grid and redacted reports rather than private comics. Paper tracing is not an actual file parse when no report exists.

Reopen and verify the two counts

Exit and return to A and B, checking complete images and actual page counts. Reconstruct pass coverage separately on paper rather than enter reader page numbers into the pass table. Retain file identities, IHDR reports, coordinates, the sixty-four-point check and observations. Explain that interlacing organises pixel transmission without adding comic pages, while unmeasured loading time stays unknown. Recalculate pass populations for new dimensions instead of applying the eight-by-eight count sequence to every PNG.

Related guides and sources

Check PNG dimensions in ManYue: separate pixel counts and pHYs density; ManYue file formats: choose CBZ, CBR, CB7 or PDF and check page order.

Checked on November 14, 2026: Apple public information lists ManYue 2.0.5, requiring iOS / iPadOS 15.0 or later. See the official App Store for published capabilities; verify specific controls in the installed version.

Method reference: W3C: PNG interlacing and Adam7 passes. Samples, passages and controls are original exercises. Sources establish definitions and checking methods rather than new automatic analysis in the app. Manual records may be kept externally, and unknown fields should remain explicit. This article does not claim step-by-step testing on a physical device, private server or every output environment.