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Need 300dpi for print book

Jul 18, 2012, 02:18
Post: #1
Need 300dpi for print book
Hi,

I've looked but maybe don't understand this...

I've got photos from the web and need to convert them to 300dpi for a book.
1) What do I need to be concerned with here and 2) how do I do this?

Thanks so much.
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Jul 18, 2012, 10:10
Post: #2
RE: Need 300dpi for print book
You need to know the final print size. If the print size is 4"x3", then you have to provide an image which is 1200x900 pixels.
Code:
print_size (inches) * print_definition (DPI/PPI) = image_size (pixels)

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Jul 23, 2012, 23:57
Post: #3
RE: Need 300dpi for print book
(Jul 18, 2012 02:18)Sarto Wrote:  Hi,

I've looked but maybe don't understand this...

I've got photos from the web and need to convert them to 300dpi for a book.
1) What do I need to be concerned with here and 2) how do I do this?

Thanks so much.


Hi,

I must be missing something here. I've got a 1" wide x 1.5" tall photo and right now the resolution is at 1050 pixels/in. I'm trying to increase the size to 1.75 x 2.75 roughly but when I increase the size the resolution decreases to 600dpi.

I tried multiplying 1.75 by 300 for 525 pixels, and 2.75 by 300 for 825 pixels but this makes a 2x3 photo. Plus, the x - y axis is fixed so I'm missing something here too.

Thanks for the help.
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Jul 24, 2012, 00:24
Post: #4
RE: Need 300dpi for print book
(Jul 23, 2012 23:57)Sarto Wrote:  I must be missing something here. I've got a 1" wide x 1.5" tall photo and right now the resolution is at 1050 pixels/in.
So your image is 1050x1575 pixels

(Jul 23, 2012 23:57)Sarto Wrote:  I'm trying to increase the size to 1.75 x 2.75 roughly but when I increase the size the resolution decreases to 600dpi.
Because 1050/1.75=600. Gimp won't change the size in pixels (unless you use Image/Scale image) because this always degrades the image quality. In "Image/Print size" you can change either the physical print size or the resolution, but since the size in pixels is given, this changes the other accordingly. 600DPI is very good print quality.

I tried multiplying 1.75 by 300 for 525 pixels, and 2.75 by 300 for 825 pixels but this makes a 2x3 photo. Plus, the x - y axis is fixed so I'm missing something here too.
[/quote]

If you need a 1.75"x2.625" photo at 300DPI then you need an image which is 525x787 pixels that you can obtain by explcitly scaling down your image (Image/Scale image).

But a 1.75"x2.75" image hasn't got the same aspect ratio... (1:1.57 instead of 1.5) so you must first crop your image to extract from it some image with the proper aspect ratio, To keep the maximum from you current image, this means an image with a height of 1575px, with a width of: 1575x1.75/2.75=1002 pixels. So you have to crop your image first, then scale it down to 525x825.

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Jul 24, 2012, 23:03
Post: #5
RE: Need 300dpi for print book
(Jul 24, 2012 00:24)ofnuts Wrote:  
(Jul 23, 2012 23:57)Sarto Wrote:  I must be missing something here. I've got a 1" wide x 1.5" tall photo and right now the resolution is at 1050 pixels/in.
So your image is 1050x1575 pixels

(Jul 23, 2012 23:57)Sarto Wrote:  I'm trying to increase the size to 1.75 x 2.75 roughly but when I increase the size the resolution decreases to 600dpi.
Because 1050/1.75=600. Gimp won't change the size in pixels (unless you use Image/Scale image) because this always degrades the image quality. In "Image/Print size" you can change either the physical print size or the resolution, but since the size in pixels is given, this changes the other accordingly. 600DPI is very good print quality.

I tried multiplying 1.75 by 300 for 525 pixels, and 2.75 by 300 for 825 pixels but this makes a 2x3 photo. Plus, the x - y axis is fixed so I'm missing something here too.

If you need a 1.75"x2.625" photo at 300DPI then you need an image which is 525x787 pixels that you can obtain by explcitly scaling down your image (Image/Scale image).

But a 1.75"x2.75" image hasn't got the same aspect ratio... (1:1.57 instead of 1.5) so you must first crop your image to extract from it some image with the proper aspect ratio, To keep the maximum from you current image, this means an image with a height of 1575px, with a width of: 1575x1.75/2.75=1002 pixels. So you have to crop your image first, then scale it down to 525x825.
[/quote]


Of Nuts,

Man, you are saving my hide! And now for my next question... is there a preferred file type to save photos in for GIMP before loading them into Openoffice Writer? Should I save them as jpeg, tff, pdf, or does it even matter?

Thanks again.
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Jul 25, 2012, 00:27
Post: #6
RE: Need 300dpi for print book
JPEG or PNG will do. This said, for inclusion in OpenOffice (or MS-Office for that matter) I wouldn't provide the exact size, but your original, because the word processor will take care of resizing the picture (Format/Picture). And if it thinks the picture needs two more pixels it may start doing naughty things to it. If you provide a picture which is too big, it will scale it down, but downscaling with factors not close to 1:1 usually go fairly well.

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