PNG maximum dimensions?

gonzo...@gmail.com

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Nov 12, 2007, 5:27:24 PM11/12/07

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I'm using a php script to generate a huge number of PNG image files.
Some of the larger PNGs are not viewable in a web browser, though-they
just show up as broken links. These ones are only viewable in
Photoshop and usually need to be cut down to around 30,000px tall (I
forget the exact number). Is this a limitation of the PNG format?
What are the maximum dimensions of a PNG image?

Richard

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Nov 13, 2007, 1:55:27 PM11/13/07

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<gonzo...@gmail.com> wrote in message
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Hi,
do you have any idea of how much memory those imgs take when displayed?

R.

gonzo...@gmail.com

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Nov 14, 2007, 2:13:21 AM11/14/07

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> Hi,
> do you have any idea of how much memory those imgs take when displayed?
>
> R.

Sure. They are all very simple 8 bit pngs. Few of them take up more
than 500kB.

Tim Roberts

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Nov 14, 2007, 2:17:56 AM11/14/07

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How many web browsers have you tested, and on what platforms?

The PNG format uses a 32-bit field to store the width and height, so that's
not the problem. However, GDI in Windows uses signed 16-bit values in some
cases for physical coordinates, which limits you to 32,767.
--
Tim Roberts, ti...@probo.com
Providenza & Boekelheide, Inc.

gonzo...@gmail.com

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Nov 14, 2007, 9:13:50 AM11/14/07

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I've tested Firefox, Safari and IE on Windows.

I guess I left out another detail, too. The app I use to create these
images "fails" halfway through creation of the PNG files, but only if
the length of the image is less than 16000px (the values could be
higher, this is just where I arbitrarily decided to split the files
into two. This app "failing" actually creates a perfect PNG image,
but as mentioned in a previous post, is only viewable to me in Adobe
PhotoShop. It's also worth noting that when the file is open in
PhotoShop, it cannot be saved back into PNG format-only BMP and other
less-desirable formats. The only way PhotoShop can save the file is
to divide it into ~30,000px parts.

I think you've answered my question with the maximum dimension being
32767. I'm just posting this bit to add to the discussion.

Thanks for the help!

On Nov 14, 2:17 am, Tim Roberts <t...@probo.com> wrote:
>
> How many web browsers have you tested, and on what platforms?
>
> The PNG format uses a 32-bit field to store the width and height, so that's
> not the problem. However, GDI in Windows uses signed 16-bit values in some
> cases for physical coordinates, which limits you to 32,767.
> --

> Tim Roberts, t...@probo.com
> Providenza & Boekelheide, Inc.

Richard

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Nov 14, 2007, 5:23:31 PM11/14/07

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Hi again,

assuming a square image, 1 image of 30000 pix would need around
30.000 * 30.000 / 1024 /1024 = 859 MB of memory to be displayed

A 24 bit = 2.7 GB of memory
A 32 bit = 3.6 GB

I am surprised that Photoshop can even open that...!
Can I ask what you need those images for? And how you manage to create them
in PHP?

R.

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