Ensure a consistent 72 dpi for Linux headless

[ariya]

ariya.hi...@gmail.com commented:

Apparently the screen resolution is not set to 72 dpi on every platform we support.

Disclaimer:
This issue was migrated on 2013-03-15 from the project's former issue tracker on Google Code, Issue #659.
🌟   12 people had starred this issue at the time of migration.

[ariya]

ariya.hi...@gmail.com commented:

Discussion: https://groups.google.com/forum/?fromgroups#!topic/phantomjs/YQIyxLWhmr0.

[ariya]

ariya.hi...@gmail.com commented:

Related pull request: #286.

[ariya]

ariya.hi...@gmail.com commented:

Rescheduled to 1.8.

 
Metadata Updates

• Milestone updated: Release1.8 (was: Release1.7)

[JamesMGreene]

james.m....@gmail.com commented:

I agree that we should provide a consistent default value of 72 for resolution (DPI) fonts, PDFs, etc. across all supported platforms. However, I also think we should provide the user with a mechanism to set their own choice DPI, as mentioned by other users in comments on the Pull Request and in forum discussions, e.g. https://groups.google.com/forum/m/?fromgroups#!topic/phantomjs/V9EU0UdT1cg

[ariya]

ariya.hi...@gmail.com commented:

Rescheduled to 1.9.

 
Metadata Updates

• Milestone updated: Release1.9 (was: Release1.8)

[ariya]

ariya.hi...@gmail.com commented:

I found that all we need is to implement physicalSize() for our minimalistic QPlatformScreen implementation. Because it was not implemented, the default 100 dpi was used and that causes the inconsistency.

[ariya]

ariya.hi...@gmail.com commented:

It's more complicated on Windows because Qt just uses the values from GetDeviceCaps and LOGPIXELSX/LOGPIXELSY. According to http://stackoverflow.com/questions/645352/is-the-number-of-pixels-per-inch-standard-on-all-windows-pc-displays-logpixels, the return values could be anything from 88, 96, 120, and maybe even more variations on the future Windows version.

I think nothing we can do about Windows for the near future. Hence, I plan to change the issue title to only cover OS X and Linux.

[ariya]

ariya.hi...@gmail.com commented:

Linux: Ensure we use 72 dpi.
3f42fb230f

[ariya]

ariya.hi...@gmail.com commented:

 

 
Metadata Updates

• Title updated: Ensure a consistent 72 dpi for Linux headless rendering

[ariya]

ariya.hi...@gmail.com commented:

 

 
Metadata Updates

• Status updated: Fixed

[JamesMGreene]

james.m....@gmail.com commented:

 

[JamesMGreene]

james.m....@gmail.com commented:

Filed Issue #934 to pursue fixing this for Windows in the future.

[ferama]

marco.fe...@gmail.com commented:

Still not fixed for me :( For some reason I still have different pdf outputs from mac os x version and from linux version

[ariya]

ariya.hi...@gmail.com commented:

What about PNG output? The PDF output relies on the print engine which may have some slight differences.

[ariya]

ariya.hi...@gmail.com commented:

With the 72 dpi change I have committed, QWebFrame::print gives zoomFactorX and zoomFactorY both to 1.

[ariya]

ariya.hi...@gmail.com commented:

Here is a test script I used:;

var page = require('webpage').create();
page.content = '

Hello

';
page.render('dpi.pdf');
phantom.exit();

The PDF results can be seen in the attachment, as well as the comparison screenshot.

 
Metadata Updates

• Title updated: Ensure a consistent 72 dpi for Linux headless

[ferama]

marco.fe...@gmail.com commented:

try this:

var page = require('webpage').create();

page.paperSize = {
format: 'A4',
margin: "1cm",
};

page.content = "

Test

";
page.render("out.pdf");
phantom.exit();

out.1.6-linux-mypatch obtained with the force dpi=72 patch added to phantomjs 1.6 (#286)

[ariya]

ariya.hi...@gmail.com commented:

Did you try with version 1.8? Unfortunately, this one did not make it to 1.8. It will be part of 1.9, meanwhile you need to build it yourself.

[ariya]

ariya.hi...@gmail.com commented:

Issue 750 has been merged into this issue.