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MakingProfessionalQualityScientificFigures:PartII– AdvancedImageEditing
RESOURCES:http://www.people.fas.harvard.edu/~draft/thesisworkshop/• PDFofthispresentation• PDFofinstructionsforimagemanipulation• Sampleimagesusedinthedemos
TipsonRasterFileFormats• TIF,PNG– “lossless”compression
– UseTIFFforyourmasterfile(original)– SaveanewcopyasTIForPNGeachtimeyouedit/manipulate
• JPEG– “lossy”compression– smallerfilesize(~10fold)withhighqualitycompression– FinalPDFwillautomaticallyconvertimagestoJPGbydefault
HighqualityJPG11KB
OriginalPNG178KB
LowqualityJPG5KB
Apixelisablockwithagrayscale intensityvalue(0-255foran8-bitimage)
000 124713
02259202843
355916405168
715232836518598111624 40597481121
1120364774999599
202951 65788787121
EditingImageFiles
Wecanviewagraphofallthepixelvalues(pixelhistogram)
0 255
#pixelswith
thatvalue
pixelintensityvalues 0 255
#pixelswith
thatvalue
pixelintensityvalues
Stretchthepixelvaluerangetocovertheentiredisplayrange
FilltheDynamicRange
Wecanadjustthehowthepixelvaluestohelptheviewerseemore‘information’
Arasterimageissimplyagridofpixels
Wemakeiteasierfortheeye todistinguishdifferencesinthedata
Howtoadjustthelevels:
0255OriginalPixelValues
255
New
pixe
lvalue
s
Quantifyoriginalimage,notmanipulatedimage.Thisisfordisplaypurposeonly
TIPS:1) Leavesomebackground(non-black)to
showtherelativebrightness.2) Don’tsaturatepixels/objectsyoucare
about(informationwouldbelost).3) Formulticolorimages,workoneachcolor
separately.
Movetrianglerighttoset‘0’value
Movetrianglelefttoset‘255’value
OpentheimageinPhotoshoporGIMP
0 255OriginalPixelValues
255
New
pixe
lvalue
s
“Bringoutthemid-tones”
Thethirdtriangle:Gamma
Movetriangle
DEMO
HowtoIEnsureMyImagesare220ppi?
• Normalprinter:220ppi/dpi(pixels/dotsperinch)• Slideshows(projects/monitors)72ppi
Easyas1-2-3
100px (10x10)
1inch
100px (10x10)
1inch 10px/in 100px/in
• Changesinppi =changesinimagedimensions.• NOCHANGEthepixelnumber
STEP1:Adjustimageresolutionto220ppianddeterminethesizeofyourimage
DEMO
1inch
STEP2:Insert220ppi ImageintoPPT
Thatwillgiveyoua1inchborderinfinaldocument
Use9inches
Use6.5inches
Insertordragyour220ppi imageintoPPT(don’tcopy/paste!)
• Theimagewillappearatproperprintingresolutionanddimensionso Iftheimageisbiggerthanyouneed,seestep3optionAo Iftheimageissmallerthanyouneed,seestep3optionB
FigureLegend
WordDoc:8.5x11
Easyway:• Drag/resizeinpowerpoint (usingtheboundingbox)
DecreasetheImageDimensionbyremovingpixels
1inch
100px (10x10)
1inch
10px/in
Actual:10px/in;1inx1in Target:10px/in;0.5inx0.5in1inch
1inch
STEP3-A:Imageistoobig
Easyway:• Drag/resizeinpowerpoint (usingtheboundingbox)• Click‘FormatPicture’>‘Compress’>220 (printing),selectedpictureonly
DecreasetheImageDimensionbyremovingpixels
1inch
100px (10x10)
1inch
10px/in
Actual:10px/in;1inx1in Target:10px/in;0.5inx0.5in1inch
1inch
10px/in
25px (5x5)
STEP3-A:Imageistoobig
IncreasingtheImageDimensions– needto‘add’pixels
1inch
100px (10x10)
1inch
10px/in
Actual:10px/in;1inx1in2inch
Target:10px/in;2inx2in
2inch
5px/in
STEP3-B:Imageistoosmall
400px (20x20)
10px/in
Note:Ifyouaretryingtoaddpixelstogiveyourimagebetterclarity/resolution(likeaCSI-Miamizoom-in),itsnotgoingtowork.Eitherrecapturetheimage,ormakethepixelatedimagebigger(seenextstep),whichcanbeusefultoseedetailsthatarethere.
Step3-B:AddingPixelsIfyou’reenlargingmicroscopepictures,don’taddfakepixelinformation(“interpolate”)yourimagewhenenlarging– youwanttoshowtherealdata!
• CAUTION:Drag/resizingtheboundingboxinpowerpoint willinterpolateyourimage!
BAD– blurred:‘information’added
GOOD– pixelated– realinformation
• Use‘NearestNeighbor’(Photoshop)or‘NoInterpolation’(GIMP)toaddpixelswithoutblurringtheimage.• ReinserttheimageintoPPT.
DEMO
Done.• Summary
- UsePhotoshoporGIMPtoadjustyourimagelevels.- Check/settheresolutionofyourimageinPhotoshoporGIMP- InsertpictureintoPowerpoint (DONOTCOPYANDPASTE!)- Scaleyourimagedownifyoulike(compressafterwardstoremoveexcesspixels).- Ifnecessary,makeyourimagebiggerbyaddingpixelswithoutinterpolationin
PhotoshoporGIMP.
