\n\n\n\n�People do not read reports. They scan them. Your layout decides what they see.�
Why pixel perfect still matters in JasperReports
\n\n\n\nI have been living inside JasperReports all week and it reminds me of print days. Kerning, grids, white space, all of it. We ship to PDF, XLS, and HTML, and the same JRXML design must hold its shape across exporters. That is the core game with pixel perfect reports. Make it look the same at 96 dpi in a browser, on paper from a laser printer, and inside Excel where cells like to snap to their own rhythm.
\n\n\n\nWith IE7 and Firefox 2 finally on more desks, HTML looks cleaner, but for contracts, invoices, and board decks the star is still PDF. And right on time, iReport gives us a decent WYSIWYG canvas while JasperReports handles the render with iText. Java 6 is almost out and the toolchain feels fast enough to care about pixels again. The promise is simple. Set rules once, get the same careful output everywhere.
\n\n\n\nA week in the trenches with iReport
\n\n\n\nI had a client ask for a compact sales summary with branded typography and a tight grid that could drop into JasperServer for scheduling. The first draft looked fine in the preview. Then the PDF came out one line longer and the XLS exporter made a mess of columns. Classic. The fix was not a new library. It was patience with bands, fonts, and spacing. Pixel perfect is a mindset more than a feature.
\n\n\n\nWhat helped was treating the report as print first. I built the layout on an 8 point baseline, used styles from the start, kept elements from overlapping, and let groups carry the story. The magic is in the details. Small flags like stretch with overflow, print when, and remove line when blank decide whether your Friday night is quiet or not.
\n\n\n\nDeep dive 1. Bands, groups, and pagination that behave
\n\n\n\nJasperReports lives on bands. Title, page header, column header, detail, footers, summary. Get these right and pagination stops being a dice roll.
\n\n\n\n- Use a baseline grid. Pick a base unit and set element heights in multiples of that unit. It keeps pages consistent across exporters.
- Keep elements from overlapping. The engine treats overlap as absolute canvas paint. XLS exporters will create extra cells and HTML can shift.
- Turn on stretch with overflow only when content really grows. For labels and constants, keep fixed heights so the grid stays tight.
- Control flow with position type set to float for content that should slide up when something above is hidden. It trims dead air.
- Let groups carry section logic. Group headers for section titles, group footers for totals. If a total must not break, enable the keep together flag on the group band.
- When a table must not split, consider a subreport with a guard band before and after. Fewer surprises than fighting the detail band alone.
Goal number one is a predictable page break. Once the break is stable, PDF and HTML start agreeing. Then XLS has a fair chance.
\n\n\n\nDeep dive 2. Fonts, metrics, and crisp PDF output
\n\n\n\nMost report drift comes from fonts. What you see in the designer may not match the JVM at run time, and it rarely matches the PDF unless you set it up.
\n\n\n\n- Pick two font families at most. One for headings, one for body. Use the same family for on screen and PDF to keep metrics aligned.
- In your styles, set pdfFontName, pdfEncoding and pdfEmbedded. For Western text, CP1252 works. For mixed scripts, use Identity H and embed the TTF.
- Install the TTF on the server that runs the report or point styles to a bundled copy. No font, no guarantee.
- Avoid fake bold or italic. Use the actual TTF variants and map them in the style. Fake styles shift spacing and break pagination.
- Watch line spacing. A body font at 9pt with 12pt line spacing is safe. Smaller lines often clip accents in PDF.
Once fonts are stable, the PDF exporter becomes boring in the best way. Text lands where the guides say, page counts match, and your brand looks sharp.
\n\n\n\nDeep dive 3. Clean XLS and HTML from the same JRXML
\n\n\n\nExcel wants a grid. Reports love decoration. To make both happy, design with an XLS mindset even if the star is PDF.
\n\n\n\n- Turn on ignore pagination for the XLS exporter. It produces one long sheet that users expect for data work.
- Use frames only when grouping elements is a must. Frames create extra cell blocks in XLS. Flat layouts export cleaner.
- Align all elements to a consistent column grid. Widths must add up cleanly. If you see many merged cells in Excel, your columns are off by a pixel.
- Prefer text fields over static text when exporting to CSV or XLS. They respect number formats and keep data types intact.
- Keep borders light. In Excel, strong borders make maintenance hard. In PDF, a soft grid or zebra stripe reads better.
- Limit subreports on rows that repeat a lot. They are fine for summaries and side panels, but on large lists they slow the export and fragment cells.
For HTML, set a body background and line height in the container page and let the HTML exporter output lean markup. Less styling in the report means fewer surprises in browsers.
\n\n\n\nNotes from the craft
\n\n\n\nThe lesson that keeps coming back is simple. Structure beats decoration. Start with bands and groups that tell the story. Pick fonts once and lock them. Avoid overlap. Then lean on styles, not one off tweaks. JasperReports is friendly when the report respects these rules and stubborn when it does not.
\n\n\n\nTools will keep moving. Browsers got better this season, Java is about to get a bump, and JasperSoft keeps polishing iReport and JasperServer. The basics do not change. Clear grid. Honest spacing. Fonts that match. With that in place, your pixel perfect reports will survive new exporters, new printers, and new eyes on Monday morning.
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