How to Resize an Image - All About Images - Research Guides

An in-depth explanation of resizing and changing resolution of digital images ... Enter new pixel dimensions, document size, or resolution. SkiptoMainContent UniversityofMichigan Library ResearchGuides AskaLibrarian UniversityofMichiganLibraryResearchGuidesAllAboutImagesHowtoResizeanImage SearchthisGuide Search AllAboutImages Focusesonmanycommonimagequestionsinregardstoimageresolutions,resizingimages,filetypes,vectorandrasterimages,scanning,savingandmore. HomeRastervs.VectorImagesColorModesImageFileFormatsScanningWhatisResolution?WhatisResizing?HowtoChangeResolutionToggleDropdownUseGIMPtoChangeResolutionHowtoResizeanImageUseGIMPtoResizeanImage PPIandDPI WhatarePPI&DPI? Thesetwoacronymsareoftenusedinterchangeablyalthoughtheydohavedifferentmeanings. PPI(PixelsPerInch)refersdisplayresolution,or,howmanyindividualpixelsaredisplayedinoneinchofadigitalimage. DPI(DotsPerInch)referstoprinterresolution,or,thenumberofdotsofinkonaprintedimage. ThisguidewilluseonlyPPI(PixelsPerInch)todescriberesolution.  Adobe.comGuides Photoshop-ImageSizeandResolution Anin-depthexplanationofresizingandchangingresolutionofdigitalimagesusingAdobePhotoshop. EnlargingImageswithPhotoshop HowtoEnlargeanImageUsingPhotoshop ImageeditingprogramslikeAdobePhotoshopareidealwhenresizingimages.EnlargementscanbedoneinPhotoshop,howeveritisrecommendedtokeepenlargementsminimalsincequalitycanbeeasilylost.Forexample,enlargementswouldbemadeforsituationssuchasoneneedingadocumenttoprintwithalargerdocumentsizeorneedtheimagetohaveahigherresolution(whileretainingdocumentsize).   1.WithPhotoshopopen,goto File>Open andselectanimage Youmayright-clickandsavethetigerimagebelowtouseitasapracticeimage. Note:Whenenlargingimages,itisrecommendedtocleanupdustandscratchesoranynoisebeforeenlargingbecausetheseitemsmaybemagnifiedinyourenlargedimage.     2.Goto Image>ImageSize   3.An ImageSizedialogbox willappearliketheonepicturedbelow.   4.Enternewpixeldimensions,documentsize,orresolution. Theoriginalimagewas10"x6.667".Letssaywewantedtoenlargethisimagetoa12"x8"sothatitcaneasilybeprintedandframed.Wewanttokeepthe300resolution,soallweneedtodoistypeinnewpixelordocumentdimensions.Inthisexample,weincreasedthedocumentwidthfrom10"to12"andtheheightfrom6.667"to8".      5.SelectResamplingMethod BeforehittingOK,wewillwanttoselectourresamplingmethod.Whatdoesthismean?Basically,Photoshopwillhavetocreatenewpixelinformationinordertoenlargetheimage.Byselectingbicubicsmaller,wearetellingPhotoshoptointerpolate(orcreatenewpixelinformation)thatwillproducethebestresultswhenenlargingimages. Bicubic(bestforsmoothgradients)-Veryprecisemethodthatcalculatestheaveragesofsurroundingpixels. BicubicSmoother(bestforenlargements)- BasedoffofBicubicsamplingandworksbestwhenenlargingimagesthathavehighimagenoise.Imageswilllooksmootherormoresoftwiththismethod.   6. ClickOK toacceptthechanges. Congratulations!Youhavenowsuccessfullychangedthesizeofyourimage! Inthisexample,weenlargedourimagebyincreasingthedocumentsizefrom10"x6.667"to12"x8"Alsonotethatthepixeldimensionschangedfrom3000x2000to3600x24000.Finally,noticethatourimagesizestartedas17.2M(megabyte)andincreasedto24.7Mwiththeenlargement.           ReducingImageswithPhotoshop HowtoReducetheSizeofanImageUsingPhotoshop TheprocessofreducingthesizeofanimageinPhotoshopisonlyslightlydifferentthanwhenenlarging.Onemayneedtoreducethesizeofanimagebecausetheresolutionistoohighforweb,thefilesizeistoolargetoe-mail,oronlyasmallimageisrequiredforaprintedpiece.    1.WithPhotoshopopen,goto File>Open andselectanimage   2.Goto Image>ImageSize   3.An ImageSizedialogbox willappearliketheonepicturedbelow.     4.Enternewpixeldimensions,documentsize,orresolution. Theoriginalimageisat300ppi.Let'ssaythatwewanttoputthisimageonourwebsite,sowewantittobeonly600x400pixelsandwitharesolutionof72ppi.First,wecanchangetheresolutionbytypingin72andthen,wecanchangethepixeldimensionsbyentering600x400asthewidthandheight.   5.SelectResamplingMethod BeforehittingOK,wewillwanttoselectourresamplingmethod.Whatdoesthismean?Basically,Photoshopwilldiscardanyunusedpixelsinordertoreducetheimage.ByselectingaResamplingMethod,wearetellingPhotoshoptoalterpixelinformationinawaythatwillproducethebestresultswhenreducingimagesizes. Bicubic(bestforsmoothgradients) -Veryprecisemethodthatcalculatestheaveragesofsurroundingpixels. BicubicSharper(bestforreduction) - BasedoffofBicubicsamplingandworksbestwhenreducingimageswhilekeepingdetailsharper.Ifimageappearstoosharp,Bicubicisrecommended.   6. ClickOK toacceptthechanges. Congratulations!Youhavenowsuccessfullychangedthesizeofyourimage! Inthisexample,wereducedourimagesizebychangingtheresolutionfrom300to72ppiandchangingthepixeldimensionsfrom3000x2000to600x400px.Noticethatwhenwereducedtheimagesize,ourfilesizewasalsoreducedfrom17.2M(megabytes)toonly703.1K(kilobytes)!         Screen/WebResolution ImagesforWeb Webimagesworkdifferentlythanprintedimages.Withprintedimages,wemustpaycloseattentiontoresolutiontoensurewegetahigh-qualityprint. Forwebimages,wemustfocusonthepixeldimensions.Lookatthetwoimagesbelow-oneis300ppiandtheotheris72ppi. (PixelDimensions300x200;Resolution 300ppi)   (PixelDimensions300x200;Resolution 72ppi) Bothoftheseimagesdisplayattheexactsamesizeeventhoughtheirresolutionvaries.Thisisbecausethepixeldimensionsarewhatreallymatterwhenworkingwithwebimages.Noticethatthepixeldimensionsofeachimagearethesameandthereforebothimageswilldisplayatthesamesizeeventhoughtheyhavedifferingresolutions.