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Losing precision

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Losing precision John Culleton 30 May 18:02
  Losing precision Roland Roberts 30 May 19:30
   Losing precision Jon Winters 30 May 19:36
200205301713.28483.john@wex... 07 Oct 20:15
  Losing precision Jon Winters 31 May 00:07
John Culleton
2002-05-30 18:02:18 UTC (over 19 years ago)

Losing precision

I have a JPEG that was scanned at say 300dpi. I reduce it in size in Gimp. Now the dpi shoots up in proportion. I want to use the reduced image on a web page where anything over 75dpi is overkill. I know I can scale back the precision when I save the file but what is the relationship if any between the percentages shown on the save dialogue and the dpi of the saved image?

Roland Roberts
2002-05-30 19:30:24 UTC (over 19 years ago)

Losing precision

"John" == John Culleton writes:

John> I have a JPEG that was scanned at say 300dpi. I reduce it in John> size in Gimp. Now the dpi shoots up in proportion. I want to John> use the reduced image on a web page where anything over John> 75dpi is overkill. I know I can scale back the precision John> when I save the file but what is the relationship if any John> between the percentages shown on the save dialogue and the John> dpi of the saved image?

If you are putting it on the web, ignore DPI. You don't care about DPI, you care about dimensions. DPI will have *no* effect on what you see for a web image.

roland

Jon Winters
2002-05-30 19:36:01 UTC (over 19 years ago)

Losing precision

On 30 May 2002, Roland Roberts wrote:

If you are putting it on the web, ignore DPI. You don't care about DPI, you care about dimensions. DPI will have *no* effect on what you see for a web image.

I used to have a web page to illustrate this. I had two 72x72 pixel images and one was 1dpi and the other was 1000dpi when you opened them in photoshop.

In the web browser, side by side, they were identical. :-)

I had to make the web page to settle an arguement.

I noticed the guy asking the question worked in a pre-press capacity... over in that world dpi is important so I can understand him asking.

Jon Winters
2002-05-31 00:07:22 UTC (over 19 years ago)

Losing precision

On Thu, 30 May 2002, John Culleton wrote:

On Thursday 30 May 2002 12:12 pm, you wrote:

Scale the image and pay no attention to the DPI. The actual width and height in pixels is what the web browser renders. No control over the DPI of the users desktop... must use absolute pixels! :-)

However, I am conerned about load time and file size. I want to degrade the jpeg down to approx. 75dpi. So how do I measure that?

Hi,

I've prepared a web page with two images. One is ONE dpi and the other is set to ONE THOUSAND dpi. Both images are 100x100 pixels.

They will appear identical next to each other in the web browser. They will also be the exact same file size and they will take the same amount of time to load.

Here it is: http://www.obscurasite.com/jon/images/dpi/demo.html

Note: Both files were saved with the exact same amount of JPEG compression. If I wanted to make them load faster I could have boosted the compression to get a smaller file size but the quality would have suffered. (gimp shows you the damage as you adjust the amount of compression... find the sweet spot and you're golden)

Now go tell all your friends... In the crazy world of html dpi doesn't matter! :-)