bjornk Posted October 20, 2015 Posted October 20, 2015 I've just posted a PNG image in this post. The size of the image is 351 KB (360,168 bytes) but the attachment utility reports it as 1.63 MB! I haven't noticed this before, could this be a problem with the site? Or is there some sort of conversion between PNG formats? PS. If I download the uploaded image, it is indeed 1.63 MB (1,714,417 bytes). The size for the above JPEG is reported correctly as 7.78 KB (7,969 bytes).
QuiteTheTail Posted October 20, 2015 Posted October 20, 2015 Strange. Probably the PNG image attachments are processed and converted before being added to the board (just an idea). Have you tried with the basic uploader (not Flash based)? P.S. I have some PNGs posted around here, and the original files still on my PC. You made me curious, I will check them and report my findings. As a side note, I noticed that PNG is advisable when the image contains few, indexed colors (e.g. a console window capture), while JPG is better for complex color palettes. Another fact often overlooked: the lossless BMP format can be compressed with an archive utility at higher ratios than the usual compressed formats (like JPG). The resulting archive will be surprisingly smaller.
QuiteTheTail Posted October 20, 2015 Posted October 20, 2015 I've just posted a PNG image in this post. The size of the image is 351 KB (360,168 bytes) but the attachment utility reports it as 1.63 MB! I haven't noticed this before, could this be a problem with the site? Or is there some sort of conversion between PNG formats? PS. If I download the uploaded image, it is indeed 1.63 MB (1,714,417 bytes). compr.jpg The size for the above JPEG is reported correctly as 7.78 KB (7,969 bytes). No filesize change for PNGs on my end.
bjornk Posted October 20, 2015 Author Posted October 20, 2015 I captured that image on Windows XP running inside a VM and saved as PNG with Paint (of XP). Perhaps that's the problem. Maybe there's a format difference? Did the same with the image above and it has the same issue. The size of the original image is 422 KB but the uploader reports it as 1.85 MB. I'm using the non-Flash uploader (I think), I don't have Flash installed. Edit: And what about the resolution difference? Both of these images are 1650x1080 but the uploaded image is 1440x900. Looks like they have been resized. Might be the reason for the size difference.
QuiteTheTail Posted October 20, 2015 Posted October 20, 2015 Edit: And what about the resolution difference? Both of these images are 1650x1080 but the uploaded image is 1440x900. Looks like they have been resized. Might be the reason for the size difference. MS Paint is not the problem (I created my PNGs with it). The resize process is almost certainly causing this. The image is manipulated, and the compression algorithm is probably different from yours (the one from MS Paint). It may be also due to applying the PNG compression twice. If you posted a smaller image, I'm sure this wouldn't happen. You can resize the image in Paint to 1375x900 (to preserve the aspect ratio) and then export it to PNG to avoid the problem. Still, I suggest using the JPG format if you care for filesize over quality. Or, simply let the uploaded image have a bigger filesize. P.S. If this is true, resizing PNG images (and perhaps other formats, needs checking) down to 900 width before posting them would save a lot of bandwidth.
bjornk Posted October 20, 2015 Author Posted October 20, 2015 It's not really a problem for me, but it may be a problem for the server, which is known to have had issues with free disk space.
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