https://bugs.documentfoundation.org/show_bug.cgi?id=167590
Bug ID: 167590
Summary: Calc: PNG export “Resolution” (DPI) setting has no
effect on image quality (only metadata changes)
Product: LibreOffice
Version: 25.2.2.2 release
Hardware: x86-64 (AMD64)
OS: Linux (All)
Status: UNCONFIRMED
Severity: normal
Priority: medium
Component: Calc
Assignee: [email protected]
Reporter: [email protected]
Description:
When exporting a sheet or a selection from Calc to PNG, changing the Resolution
(DPI) value in the PNG Options dialog (e.g. 96 vs 300) does not change the
actual pixel dimensions or visual quality of the exported image. Only the
stored DPI / pixels-per-meter metadata inside the PNG changes. Thus users
cannot obtain a higher-resolution (more pixels) raster image through this
control.
This is unexpected because the label “Resolution (DPI)” implies the image will
be rendered at that resolution (more pixels for higher DPI) rather than simply
writing different metadata.
If this is intentional, the UI should clarify that the field only sets
metadata. Otherwise, the export should scale the pixel output accordingly (or
provide a separate scaling control).
Steps to Reproduce:
1. Open LibreOffice Calc.
2. (Optional) Enter some sample data and formatting—e.g. fill A1:E30 with
text/numbers so output has detail.
3. (Optional) Select a range (or leave nothing selected if you intend to export
the entire sheet).
4. Choose File ▸ Export… (or File ▸ Export As ▸ Export… depending on UI),
select PNG as the format; enable Selection if you only want the chosen cells.
5. In PNG Options, note the displayed Width/Height (in pixels) and set
Resolution to 96 DPI. Export (File A).
6. Repeat export, identical steps, but set Resolution to 300 DPI. Export (File
B).
7. Compare File A and File B: check pixel dimensions (e.g. with file
properties, ImageMagick identify, or any image viewer) and visually compare.
Actual Results:
File A and File B have identical pixel dimensions and virtually identical file
sizes.
Visual appearance is the same (no increase in detail or sharpness).
Only the DPI / pixels-per-meter metadata differs (in PNG tools display it as
“Resolution”).
Therefore the “Resolution” field does not influence rasterization—only
metadata.
Expected Results:
Increasing DPI should proportionally increase the rendered pixel dimensions
(e.g. 96→300 DPI roughly triples pixels per inch, generating a larger image for
higher-quality print or downstream scaling).
Reproducible: Always
User Profile Reset: No
Additional Info:
Version: 25.2.2.2 (X86_64) / LibreOffice Community
Build ID: 520(Build:2)
CPU threads: 8; OS: Linux 6.8; UI render: default; VCL: gtk3
Locale: cs-CZ (en_US.UTF-8); UI: en-US
Ubuntu package version: 4:25.2.2-0ubuntu0.22.04.1~lo3
Calc: threaded
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