As long as you know that you're going from 16M colours to 256. Re: PNGs, by going from 24bit to 8bit, you are discarding a lot of colour information. For one, IO uses better and more up to date encoders, I'm next to certain that IO employs both Guetzli and MozJPEG (BTW, unless you're encoding using Guetzli at a q90ish or greater, you're fine w/ MozJPEG + it's Guetzli is slow, something that even Google has acknowledged), and as you mentioned IO will take care of other things that PS will not - like sub sampling.
I would send it right to IO afterwards and pick the quality you need there (as you can set that).
I would then save it w/ the edit and resolution you needed and at hi q. 1st PS for the sizing and whatever ever photo editing needs you might have. Hey Jeffrey, wanted to kindly point out a few items:įor JPEGs, I would likely go from PS right to imageOptim. The image that appears in the email is as compressed as it can be. After the artwork is completed in Photoshop and exported into the email's image directory, our tools detect the image and automatically run the optimizations behind the scenes. Then we run through ImageOptim in lossless mode. Then we run the through lossless ImageOptim.įor GIF, we Save for Web and painstakingly tweak until we've gotten the color count to an absolute minimum We use GIF just for line art and logos - so we're usually able to get the color count down to between 4-10. Then we follow up with ImageOptim in lossless to squeeze the last unnecessary bytes from the image.įor PNG, we save out of Photoshop using SuperPNG, converting 24bit with transparency to 8bit with transparency. They often optimize images in different, mutually beneficial ways, but for some images, the result is slightly larger so our automated system runs them sequentially and only uses the results when the image is smaller. Then we run lossy Google's Guetzli AND/OR* MozJPEG. We have different image optimization routines based on the type of image.įor JPEG - first, we use Photoshop's Save for Web at 50-60% quality. Let's also add the fact that images need to be decoded, and the larger the image, the greater the decoding tax (time) - which is a strain on the processing.Įssentially, going with images that are excessively too big is a lose lose. So no matter what the container size, you're faced w/ massive memory usage. On a more tech level, an issue that plagues mobile devices is the abundance of poorly sized images, and how they contribute to crashing devices (esp on android). On a non technical level, the sad surprise will be when your user goes to save the image - which we know they do, and it will be saved at the very poor quality you provided, in it's large original size, something that might just send marketing and their branding dept in turmoil. This is a technique that was discussed some time back, but you run into several challenges. W/O getting into excess details, something like ImageOptim will take care of both for you. I mentioned this my #LitmusLive talk, but there are a few things that you want to deal with using PS exported images: metadata, and the sub sampling. The smaller the dimensions, the more you might be able to get away w/ lesser quality.Īlways use something like ImageOptim. And the dimensions of the image will also play into this. The quality gains at 80+ are less perceivable, but you'll suffer from file size. The JPG is a lossy format by default for one, and for 2, once you pass 80ish% quality setting, there's a diminishing return in quality vs size. My recommandation is to never ever save 100% quality. Don't use JPGs for image text (text images?), that's not where it's strength is - doesn't handle sharp changes in contrast to well. Do recall that JPGs are meant for pictures/photos, and possibly smooth gradients. But PNGs are a lossless format (large file size), you do need to be careful when using them. Many forget that you have a PNG-8 to your disposal (256 colours or less), and depending on the amount of colours, this can be a GREAT option. Hey Kev, I agree w/ what was said below - but I would add a few items:Īlways consider the format you need to start with.
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