GIMP 2.10 Tutorial: Scale Images with Minimal Quality Loss

[Music] [Music] hello and welcome to yet another tutorial by Davies media design my name is Michael Davies and in today's tutorial I'll be showing you how to scale images up or down with minimal quality loss I say minimal because a lot of tutorials out there claim to show you how to scale an image up or down without quality loss that's actually not really possible given how the process works for scaling images up or down so any video out there really that says it's going to be able to achieve a larger or smaller image without quality loss is really just exaggerating the truth or flat outline anyway I'm using version 2.2 0.6 for this tutorial which as always is the latest version of at the time of this tutorial but of course before we get into all that I want to direct you guys over to my website at Davies media design.com as always we have tons of give video and how-to articles on here so definitely check that out you can also enroll in our photo editing course from beginner to pro photo retoucher which is a bestseller on udemy and of course you could support our channel and help us grow by becoming a patron on patreon and you'll get tons of awesome extras in return and I'll include a link to this as well as all the relevant links from this tutorial in the description of the video all right so we're gonna be covering a ton of concepts in this tutorial just in terms of image size and general image resolutions the difference between your image size on your computer screen versus in a print scenario like if you were to print this on a piece of paper and scaling concepts such as interpolation and resampling so I want to start with the differences between how your image is displayed here on your computer screen versus how your image is going to be displayed in a print environment and I'm going to demonstrate that through a poster that I design in my Magdala Lopez style poster tutorial which of course I'll link to in the description of this video but here was that final poster and this is actually the JPEG form so I actually have two versions of this so I have the 25 50 by 30 300 300 PPI version of this and I know it's 300 PPI because if I go to image image properties you'll see here we have the size in pixels and then we also have the print size and then we have the resolution which is 300 by 300 PPI and I'll hit close on this for those you don't know the resolution is set when you're going to file new and you're opening up a new image and under Advanced Options you choose the X&Y resolution as 300 however you can also change the PPI by going to image scale image and then right here there's X&Y resolution and this one is set to 300 PPI and you can actually change the unit of resolution here so right now it's PPI you also have pixels per millimeter pixels per yard and so on if you have a specific unit that you need for your print job I'm just going to exit out of that so this one over here is the same exact size image 25 50 by 30 300 except the PPI is set to 72 pixels per inch and you could tell that again by going to image image properties and here you'll see the size and pixels is 25 50 by 30 300 pixels but the print size is actually much larger it's 35.42 by 45.8 3 inches and the resolution is 72 by 72 pixels per inch so you'll notice here the print size is actually much larger for this one and the reason being that when you have a lower resolution but you have the same size in pixels basically because you have less pixels per inch these pixels are going to be able to spread out more and cover more area so if I were to print this the print quality would be lower overall but it would be able to cover a larger area so it would be able to cover a 35 by 45 inch piece of paper or whatever you were printing this on but in terms of displaying this on the screen or displaying this for web you'll see that there is no difference here between the 72 pixels per inch version of this and the 300 pixels per inch version so there's not going to be any difference really on our computer screen which is why when you're saving this for web you want to just save this as 72 PPI because even though it's a lower resolution nobody's gonna be able to tell and the file size is gonna be smaller all right so moving on from that concept I'm gonna come over to my next image here and this is an image that I took with my camera and you'll see up here that this image is around 3,500 by 5,000 pixels give or take of course I do have four of these open and these are all the same exact image and the reason I have four different versions of the same image is I'm going to demonstrate different versions of interpolation for those of you who aren't familiar with the term interpolation anytime you enlarge or shrink an image down it's going to cause to fill in missing pixels or just change the overall structure of the pixels via a method called interpolation no new detail is added during this process which is why there is quality loss when it comes to scaling an image so it's either removing pixels from your image when you're shrinking the image down or it's adding in brand-new pixels in between the existing pixels when you're scaling something up so anyway in a nutshell interpolation is how your image editor figures out how to represent your picture after scaling it up or down so let me show you how to scale your image you go to image scale image this is always how you scale an image within if you use the scale tool over here you're only scaling the active layer path or selection so scale image is going to scale the entire composition you'll see here you have your width and height and you've got a little chain icon here you want to usually make sure this is locked so this is unlocked this is locked anytime you have it locked it's going to keep the original aspect ratio of the image so that's just gonna keep your image from looking stretched or wonky when you resize it you've also got some units here so you can scale this based on percent pixels inches millimeters etc so you've got a bunch of different types of Units there and then of course you've got your X&Y resolution here I have this set to 72 right because I'm only gonna be using this for the web I'm not gonna be using this for print you'll also see an option down here called quality and then you have interpolation if you click on this you have several interpolation types so this is what I was talking about when it comes to adding or removing pixels in your image so these are just the various methods that are used to perform that interpolation action and try to preserve quality while you're doing that these also correspond to the performance of on your computer so when you have this set to none it's going to preserve the least amount of quality in your image when you're scaling up depending on the situation of course but usually this is going to preserve the least amount of quality in your image so it's going to show the most amount of artifacts however it will be the fastest form of scaling so if you have a very slow computer and you don't have time to sit there and wait for the image to finish scaling up or down you can set it to this option so it'll be the lowest quality but the fastest performance on your computer and as you move up linear and cubic are just progressively better at preserving the quality in your image but get progressively slower in terms of performance and then you get into what I call the next generation of interpolation within which is no halo and low halo and these two are the best forms of interpolation within and that's just sort of a consensus within the community the reason why they're called no halo and low halo so low halo actually came first and it was created basically to minimize the effects of something called haloing which happens around text and just other areas of your image when you scale up or down so the goal of this is to minimize that haloing and to get rid of as many artifacts without losing the sharpness or just overall quality of the image no halo is sort of the next generation of low halo it does the same thing as low halo it gets rid of haloing effects within an image but it just uses an upgraded technique to try to do a better job cleaning up the image in the same way that low halo does no halo is said to be best used when you are not scaling an image down too much and that's typically below 50% of the original image size it's also best when scaling images up that do not contain lots of text or pixel art or when skin tones need to be preserved in the image so I typically use no halo when I'm scaling images up or down because I work with a lot of photos that have models in them or subjects in them and so typically you're wanting to preserve those skin tones and I don't typically have a ton of text in my images either low halo on the other hand is best used when scaling an image to less than half of its original size or when scaling images up that contain lots of text pixel art or noise and/or artifacts so the best way to minimize quality loss is through the selection of the proper interpolation method based on the type of image that you're trying to scale and then you can also combine these interpolation methods with the sharpen filter if you really need to alright so now that I've gone through all the boring technical details about scaling and interpolation quality I'm gonna show you guys a few examples here of how this looks based on which one we select so I'm gonna start with none keep in mind for this quality setting how quickly this scales this image down and by the way I am scaling all of these images here down at first because these are all pretty large images and then for the scaling up portion I'm gonna use another photo here so with my interpolation set to none I'm gonna scale this down to 10% of its original size and if I hit the tab key that will automatically scale my height as well with the same aspect ratio and I'll hit scale so you'll see that scaled very quickly I didn't speed the video up or anything and I have my zoom tool selected here and I've got this set to 12 and a half percent right now we're gonna zoom all the way in on this and then zoom in a bit more so we'll go with five hundred and fifty percent zoom for this image so you can see it's very pixelated in here you can't really see a lot of detail going on here this is as to be expected when scaling an image that was that large down to this small of an image now but now we're gonna come over to our next image and perform the same thing but with a different interpolation quality so go to image scale image and I'll choose 10 percent here and hit the tab key set interpolation to linear so this is slightly better and it should be slightly slower now and I'll hit scale and then I'm just going to change this to 400 percent and then click one more time to get to 550 so you'll see here this is not quite as pixelated as our first one so this is with none and this is with linear so it's a little bit smoother here and one thing to note these quality settings do use an anti-aliasing feature that's why this is sort of smooth so it's trying to smooth out those rough edges of these pixels so this is without any of that anti-aliasing and this is with a little bit and of course it uses a little bit more complicated formula than just anti-aliasing but that is one of the major features of these interpolation quality settings so now I'm going to come back here and I'm gonna do the same thing image scale image 10% hit the tab key and I'm going to change the interpolation to cubic and I'll click scale and I'll just change just a 400% zoom and I'll zoom in one more time so we're at five fifty so here we go we have none linear and then there's cubic so the differences between linear and cubic aren't nearly as noticeable and really it's hard to tell that there is any difference at all between those two but again there is a major difference between no interpolation there so I'm going to come over here to our fourth image and I'm gonna go to image scale image and I'll hit 10 Tab key set this to no halo this time and hit scale so you'll see that one took a little bit longer and I'm going to use my zoom tool to zoom in a little bit and let me go to four hundred one more click so here you'll see this is the cubic setting and here is the no halo setting so it is marginally better so the final image is a little bit smoother it looks a little bit nicer and I'm gonna actually open up one more instance of this image and then I'm going to go to image scale image and now I'm gonna use the recommended setting here which is going to be low halo since we are scaling this below 50% of the original size and I'll hit scale and I'll zoom in we'll go to 400 click one more time so here you'll see the quality is pretty good on this one if you compare it to no halo there's really not much of a difference here and the main difference is there's no text in this photo or artifacts really so that's where you'll notice a lot of the difference between these two interpolation settings but you'll see that these two settings are by far the best settings when it comes to the final overall image so there is no halo and this is with none so you can see there's a major difference there I could sharpen this back up after I scaled it down to try to recover some of that original sharpness from the image that we lost during scaling and of course I could just do that by going to filters enhance sharpen and I can add just a little bit of sharpness to this I don't want to overdo it because it will introduce a little bit of haloing but here's a before here's an after I'll click OK and hold ctrl and zoom out a little bit and now the image looks a little bit sharper alright so let's get into scaling images up so I'm going to come over here into this image first and what I'll do is I'll scale this up by double the size and I'm gonna do that for all three of these except I'm not going to go through the cubic in linear for this image I'm just going to go through the no halo and low halo compared to none so let me go to image scale image and I'll scale this up to 200% and hit the tab key I'm gonna hit none as the interpolation quality and I'll hit scale and then I'll use my zoom tool to zoom in here I'll just go with 400% for this one and I'm gonna come over here to my next image and do the same thing so image scale image and I'll type 200 hit the tab key this time I will use no halo and hit scale and I'm gonna zoom in until we hit 400 percent there and then I'll do the same thing here so image scale image 200% hit the tab key and then change this to low halo this time and hit scale so you'll see low halo and no halo took a little bit longer to complete the scaling so remember no halo is better for when you're scaling images up especially when they don't have text or artifacts and also when you're trying to preserve skin tones and images such as this one so we do have a model and obviously she's got skin tones here let me just zoom in to 400% so this one is the low halo effect here this one is no halo and this one is none so the none obviously has a lot of pixelation going on here in the eye and if I click one more time you can really see that and so let me do that here as well so a lot less pixelation going on here everything looks a little bit more tidy in terms of the quality and if I come over here the differences are very minut if you can really see differences at all so really both the no halo and low halo options works for this photo but I would just stick with no halo unless you have text within your photo so next I'm going to come over here to my other image which has a bunch of text in it it's a lot smaller of an image so this is 165 by 165 this is actually my youtube channel icon that's been shrunk down for another social media platform I'm gonna come over here to my zoom and just change the zoom to 100 so you guys can see the original quality and the original size and I'm just gonna scale this up to about 5 times its original size so I'll go to image scale image and remember for the interpolation or the resampling method what needs to happen here is needs to basically blow up the size of this composition and then because that's going to create a bunch of negative space since there's gonna have to be a lot more pixels it's going to have to fill in those spaces using these resampling methods or the interpolation method I'm just gonna choose 500 as the width and hit the tab key and I'm actually going to change the resolution of this down to 72 just to save some space while we do this and then I'm gonna change the quality to none and I'll hit scale so now this is a hundred percent you'll see the edges of my text are really jagged here the overall quality of this actually doesn't look too bad considering we scaled it up so much but I'll zoom in here on the text you guys can see there's just kind of a bit of a mess going on here with all the pixels it's not smooth at all and you could definitely tell that this was a smaller image that has now been made a much larger image so now let me come over here to our other image this is the same exact image same exact size and now I'll go to image scale image scale up to 500% and just change this to 72 again this time I'll set the interpolation to no halo and click scale so you'll see that now there is a lot more smoothing going on it does kind of make the photo look a little bit blurry so here is our other image and let me just zoom out it looks a little bit more crisp but it also looks a lot more pixelated this one looks smoother but it looks more blurry so there's definitely trade-offs and I think in this case it kind of comes down to preference and then I'll come over here to our last instance of this photo and go to image scale image I'll choose 500 as the width and hit the tab key change this to 72 and then I'll change the interpolation quality to low halo and remember this is the recommended setting whenever you have artifacts in your image or text and I'll hit scale so here's a comparison here is with no halo and here's with low halo so low halo actually has even more smoothing going on here then no halo does so no halo still looks a little bit more pixelated in comparison to the low halo but again there is a bit of a trade-off because you might perceive that as it being blurry but I do think this looks a little bit better and it helps to minimize some of the obvious nough step this has been scaled up so this one you can obviously tell was scaled up it used to be a smaller image super pixelated this one looks a little bit better if you really want you can go to filters enhance sharpen unsharp mask so here's a before and here's an laughter so this will sharpen this up a little bit that's obviously optional I'm just gonna hit cancel there so I'm going to show you one last example of scaling an image up and then scaling an image down using no halo versus low halo so come over here to this image again that we started with and this image is a great example because if I grab my zoom tool and zoom in we not only have text but we also have a lot of these artifacts in here these of course were added on purpose this is an effect that I use within to create these pixels but what I'm gonna do first is I'm gonna scale this down and I'm gonna do that to two of these images so I'll scale this one down using the no halo effect first so I'll scale it down to 10% of its original size and I am just gonna change the resolution real quick so this one I'll use no halo as the interpolation and I'll hit scale and I'll change the zoom here to 400% so here's a close-up look of this and then I'm also going to scale this one down so go to image scale image 10 percent 72 and I'll change this one to low halo and hit scale and then we'll change this to 400% so if you compare this composition of this one the only real noticeable difference is in these little artifacts you could see that these are still a little bit more pixelated so they're a little bit more prevalent whereas over in this case they're a little bit more smooth so again this was the low halo effect and this one was the no halo quality interpolation everything else so it looks almost exactly identical to that is really the one major difference between these two it looks like low halo just has a little bit more smoothing going on whereas no halo will add a little bit of sharpening at the end there and I'm going to come over here and scale these two up so I'll go to image scale image and I'm going to scale this one up to 300% so three times the original size and I'll change this one a no halo to start so it's basically telling me this is going to create a huge image but that's alright all right so that went ahead and scaled our image up it did take a few seconds to get that done probably about 10 to 15 seconds there I'll put the exact timing on the tutorial but you can see actually everything about this is pretty high-quality despite it being three times the original size and I can actually zoom in here all the way this is a hundred percent this actually looks really good considering we scaled it up to three times its original size and the text looks pretty good as well so now let's do the same thing over here that was with the no halo effect this time we're going to use low halo so I'll go to image scale image 300 and I'll hit low halo hit scale all right so that's how I counted and it was about 35 seconds I'll compare that to the no halo I'm sure it was probably about the same I just kind of guessed the time wrong again if you zoom in here this does look pretty good so here we're at a hundred percent so the quality of this is overall really good the lettering looks pretty good and the text looks pretty good so let's see if we can zoom in on the same part of the text here so this is with no halo and this is with low halo so actually no halo looks a little bit more crisp than the low halo does and then if we zoom in on these letters right here you can see there's sort of pixels spilling off of the numbers here but come down here to the same spot so the two interpolation qualities look almost identical I would say no halo has crisper edges on the numbers here whereas the low halo effect has a little bit more smoothing going on around the outside of the numbers here so you could say that either looks less pixelated or more blurry or just has more anti-aliasing on it so it's really up to your interpretation and it's up to your preferences as to which one you prefer when you're scaling your images up or down but I think at the end of the day if you go with no halo or low halo as your interpolation quality you can't really go wrong so hold ctrl and zoom out all right so that's it for this tutorial hopefully you enjoy it if you did please subscribe to our YouTube channel at youtube.com slash Davies media design you can also visit our website at Davies media design.com you can enroll in our photo editing course from beginner to pro photo retoucher on udemy and you can support our channel and help us grow by becoming a patron on patreon and get some awesome extras in return I'll include a link to that as well as all the relevant links from this tutorial in the description of the video so thanks for watching and we'll see you next time

Channel: Davies Media Design

Views: 155,392

Keywords: gimp, gimp tutorial, gimp for beginners, how to gimp, gimp graphic design, gimp photo editing, gimp 2018, GIMP 2.10, GIMP, basics, scaling images, scale images without losing quality, lossless scaling, GIMP scale tools, scale image in GIMP, GIMP 2.10.6, GIMP basics, GIMP feature overview, how to scale an image, interpolation, lohalo, nohalo, cubic, linear

Id: Qk3BP8vzPdY

Length: 22min 46sec (1366 seconds)

Published: Wed Oct 31 2018