That is, convert every block of 8×8 pixels (64-pixel values) to 64 coefficients, which convey the block’s information in a different way. Do mathematical magic, called Discrete Cosine Transform (DCT), with the pixels.Because the human eye is more sensitive to distortion in luma (brightness) than to that in chroma (color), JPEG handles channels separately and, optionally, downsample the chroma channels to half the original resolution-a process called chroma subsampling. Instead of Red, Green, and Blue channels, JPEG works with a luma (Y) channel and two chroma channels (Cb and Cr). JPEG performs two transformations for lossy compression:
That’s all there is to know about saving GIMP files as JPEGs! If you get really curious about the advanced options, I’d be willing to try learning about the math behind them and writing up a post – or at least telling the story of how it makes no sense to me.What’s the Magic Behind Progressive JPEGs? Progressive JPEGs can start displaying before the whole image is downloaded, but the technology is intended for outdated connection speeds. Optimize applies an additional compression algorithm for bit-depth in the hope of reducing file size, and the Progressive setting only matters for online downloads. The only exceptions are that you may need to disable the Optimize setting or the Progressive setting, but leaving them on by default shouldn’t affect your image negatively in any noticeable way, so it’s simpler to just ignore them. Only joking about this last guide 😉 The Advanced Options section of the JPEG dialog is so advanced that if you actually have a reason to use any of them, you’ll already know what the settings are for, and how best to use them. The Seriously Precise Guide to Saving GIMP Files as JPEGs If you’re batch processing images with the GIMP plugin, it’s a good ‘all-purpose’ setting to use. Unless your image has a very wide range of colors, it should strike a good balance. Sometimes it helps to unfocus your eyes just a tiny bit, so you can spot the compression patterns more easily as they spread across similar color areas.Īs I said, there’s a bit of an art to it – but if you don’t want to take the time, just slide it down to 60 and call it a day. The changes can be subtle, so move the slider slowly downwards and compare the effects.
If you’re saving images for the web or social media and you care about page load times (Google does, so you should too), then you’ll need to take some extra time to find the right balance between file size and image quality.Ĭheck the box Show preview in image window to see the effects of the slider. If you’re saving photographs, you probably care most about image quality regardless of file size, so you should just leave it up at 100 and call it a day. If you want to save as any other popular file type like JPG, PNG, or TIFF, you have to use the Export As command. I’m not sure why the developers designed things this way, but the Save and Save As commands now force you to use the XCF format. You’re done! You’ve saved your GIMP file as a JPEG image.ĭon’t feel bad if you’re surprised by how easy it is. Step 3: Select JPEG as the file type and configure your compression settings. Step 2: Choose Export As from the File menu. Step 1: If you don’t already have your image open, open your XCF file (XCF is GIMP’s native file format) The process is actually quite easy, once you know that you should be using the Export As command instead of the Save command: The Quick Guide to Saving GIMP Files as JPEG The developers implemented this change as a part of GIMP’s big 2.10 update, and it’s confused a lot of people since then. The biggest – ok, the only – trick to saving GIMP files as JPEG is that you need to use the Export command instead of any of the Save commands. But it might surprise you to learn that they’re not all created equal, even when you’re saving a GIMP file as a JPEG. They’re small, high-quality, and compatible – the perfect choice for using and sharing online. JPEG files are the most popular digital image format by a large margin.
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