23 May 2019 at 9:32 pm #574331
Is it possible to view the images at full res when you hit the enlarge image button. Invariably the enlarged image is the same size as the original?
Martin23 May 2019 at 9:54 pm #581070Richard MilesParticipant
No – I don’t believe you can.
Richard24 May 2019 at 8:55 am #581071David BaseyParticipant
Is this what you mean when you hit the expand button? https://britastro.org/node/15748
David.24 May 2019 at 6:33 pm #581074Peter MulliganParticipant
If you click the expand image button, and then click on the image itself you get a slightly zoomed view. Try it on your April 20th image of Mercury. it doesn’t seem to work on every image
Peter26 May 2019 at 10:28 pm #581094
It would be great if it did that but generally the image is hardly any bigger. Why is that one different?
Martin26 May 2019 at 10:33 pm #581095
That’s interesting. I wonder why some enlarge further when click and for others nothing happens? Curious. Some of mine are uploaded as jpegs and some as pngs- will see if it relates to that.
Thanks for the suggestion anyway, Peter
Martin28 May 2019 at 9:04 am #581105David BaseyParticipant
I think it probably depends on how large the image is when you upload it. The ‘expand’ option seems to display the image at the original size. For example my Ptolemaeus image is 1200×1755 pixels and the expanded image displays as that while on the pre-expand screen it is scaled down to fit. Consequently one appears larger than the other.
Your last image of Mars seems to be 500×550 and displays as that when expanded but does not need to be scaled down on the previous screen and therefore appears the same size in both.
David.2 June 2019 at 10:42 am #581109Andy WilsonKeymaster
Apologies for the time it has taken to respond. I wanted to run my own tests before replying to be sure I was giving you accurate information.
The quick answer is the enlarge button will show a larger image if the image has been made smaller to fit webpage that shows the image and associated information. Also, large images are not recorded at the original resolution in the website.
The BAA website is built using Drupal. When images are uploaded Drupal will sometimes shrink images and may also reduce the image quality to make the image file smaller. We do not consider the member pages a formal image archive for storing images, rather a place to share observations and other interesting astronomical images. A formal image archive would not compress images, but would be a large project and probably not use Drupal.
I’ve run some tests by uploading a fairly large image of the Astronomical Clock at Exeter Cathedral.
I created both jpg and png versions of the image, though I have only left the jpg version on the website. The original image is 2008 x 2443 pixels, with the jpg version 1.28 MB and the png 5.66 MB.
After I had uploading both versions I clicked ‘expand image’ and downloaded the new image. Both jpg and png had been resized by Drupal to 1355 x 1648 pixels, with the jpg image being 246 KB and the png 2.61 MB. However, I uploaded the same jpg image twice during this process and the first time Drupal retained the original size of 2008 x 2443 pixels but reduced the image quality so it was only 530 KB.
Note, while I think this is mostly due to how Drupal works, it is possible that different browsers will give different results. I used Google Chrome on a Windows 10 computer for these tests.
Andy (member of the Website Operations Team)2 June 2019 at 10:53 pm #581110
That is a very comprehensive reply and very helpful.
Thanks for your testing,
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