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[Solved] jpeg files at 300 dpi

PostPosted: Tue Mar 10, 2015 6:33 pm
by TishAnn
I have Open Office version 4.0.0 installed on my laptop. When using the Draw program, when I export the file to a jpeg file, although the original photo is at a resolution of 300 dpi, and I specify within the Draw program itself to keep the photo at 300 dpi, Open Office automatically changes the file to 96 dpi. The 4.0.0 version of Open Office Draw allows us to specify exactly what resolution we want the photo to be exported at. However, the program overrides my specifications and automatically changes the file to 96 dpi. Is there an extension available that corrects this problem, or does a newer version of Open Office Draw actually work properly?

Thank you!

Re: jpeg files at 300 dpi

PostPosted: Tue Mar 10, 2015 7:04 pm
by acknak
Greetings and welcome to the community forum!

TishAnn wrote:... when I export the file to a jpeg file, ... Open Office automatically changes the file to 96 dpi. ...

Using AOO 4.1.1, exporting a drawing to an image doesn't seem to use the dpi value at all. It seems you have to set the pixel size directly.

Of course, ppi is just a number. The only thing that really matters is the pixel size of the image. The dpi can be anything, depending on the printed size of the image.

The results will also depend on the resolution of any images contained in the Draw document. You can't insert images at low resolution and export them at 300 dpi. Well, you can, but the images won't look good in the exported image.

Re: jpeg files at 300 dpi

PostPosted: Tue Mar 10, 2015 8:48 pm
by TishAnn
The original image that I inserted into the Draw document is 300 dpi. The pixels are 5245 x 5582. I'm wondering why Open Office Draw version 4.0.0 even bothers allowing us to insert a dpi value if it doesn't even function properly.

Re: jpeg files at 300 dpi

PostPosted: Tue Mar 10, 2015 10:50 pm
by acknak
The built-in image export is a fairly new feature. I assume it just hasn't had all the glitches ironed out yet.

I don't see a problem exporting the image at 300 dpi, you just have to do the math yourself to find the appropriate pixel size. Again, the dpi setting isn't what determines the image resolution. It's the numbering of pixels.

If you do need the 300 dpi setting on the image, export the image from Draw and use an image editor to set the dpi.

Re: jpeg files at 300 dpi

PostPosted: Wed Mar 11, 2015 4:58 pm
by TishAnn
I ended up exporting it from Draw at 96 dpi and used an old Hewlett Packard software called Image Zone to set it back to 300 dpi. How do I figure out the pixel size so that I can ensure that I have 300 dpi? I'm not sure what the pixel size would need to be.

Re: jpeg files at 300 dpi

PostPosted: Wed Mar 11, 2015 6:41 pm
by acknak
You need to know the final output size, in inches.

If the output size is ten inches, and you want 300 dots per inch (dpi), then the image must have 10*300 = 3,000 dots (pixels) across the width. So when you export from OO Draw, make sure the width in pixels is 3000.

Re: jpeg files at 300 dpi

PostPosted: Wed Mar 11, 2015 7:26 pm
by TishAnn
The width of the front cover of my book that I'm designing is 5 inches. So, the image must have 1,500 pixels across the width. I experimented with Draw and exported it as a jpeg, changing the width to 1,500 pixels and the resolution to 300 dpi. However, I checked my jpeg file after exporting it, and Draw dropped the resolution down to 96 dpi. It kept the width at 1,500 pixels, but it dropped the dpi down to 96.

Re: jpeg files at 300 dpi

PostPosted: Wed Mar 11, 2015 10:06 pm
by acknak
It is confusing but the dpi value really doesn't matter. It's just a number. If you have an image 1500 pixels wide which is printed at 5 inches wide, then it is 300 dpi no matter what the "dpi" value in the file says.

If the software at the printer's end is confused by a dpi setting other than 300, then you may need to change the dpi setting in the file to match what the pixel size and output width actually are.

You might think of it this way. Suppose I had an image, 300 pixels wide. The dpi setting in the file is 300 dpi. I insert two copies of the image into the same drawing. One copy I scale to be 4 inches wide, the other I scale to be 2 inches wide, then I print it out.

What is the dpi of each image in the printed drawing?

The first one is 300 pixels over 4 inches, or 75 dpi.

The second one is 300 pixels over 2 inches, or 150 dpi.

Neither matches the 300 dpi setting stored in the file. The dpi setting is just a number

Re: jpeg files at 300 dpi

PostPosted: Thu Mar 12, 2015 4:31 pm
by TishAnn
Thank you for your explanation. It has been very helpful.