Bonus CH-01 Line Art

8/8/2019 Bonus CH-01 Line Art

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Courtesy of Regina Cleveland


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Only those who have the patience to do simple things perfectly will acquire the skill to do difcult things easily.

Johann Schiller, German poet and playwright

Line Art Scanning

Scanning line art is a wonderful opportunity to learnhow to do a relatively simple thing perfectly. Line art im-ages consist of black lines on a white background. You seeexamples of line art every day in the text, logos, and signa-tures that are all around us. Youd think that scanning thistype of image would be simple; after all, its only pure black

and white, right? Well, in order to really get control over your line art images, youll need to go through a few hoopsin Photoshop, but with a little effort, you can achievestunning results.

Almost all scanners have a Line Art mode that gives you apure black and pure white end result. However, dont befooled by your scanner. Scanning in Line Art mode producesan image that doesnt contain anywhere near the amount of detail found in the original ( Figures 1.1 and 1.2).

If you scan an image in Line Art mode, it will open inPhotoshop in Bitmap mode, which is Photoshops modefor dealing with pure black and white images. Thats practi-cally useless, because Photoshop is not able to enhanceimages that are in Bitmap mode. (For example, you cant use most of the editing tools, rotate the image in preciseincrements, or apply lters.) This is why so many peopleend up with line art reproductions that have jagged edges,broken lines, and dense areas that are all clogged up.

Not all scanners use the samenames for their scanning modes.Line Art mode might be paradingaround under a different name,such as Text mode.

Figure 1.1 A raw line art scan.

Figure 1.2 Line art scanned using thetechniques in this chapter.


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Chapter 1 Line Art Scanning

But thats not going to happen to you. Youre going toignore your scanners advice and scan in Grayscale modeinstead of Line Art mode. After the image is scanned inGrayscale mode, you can take full advantage of Photoshopsenhancement controls. With very little practice and ahandful of tricks that youll learn in this chapter, youll beable to create beautiful line art reproductions as they wereintended to bewith crisp edges and sharp detail.

When youre done producing your line art and are pleased with the result, you should convert your image into Bitmapmode. This will keep your le size small and prevent youfrom accidentally adding shades of gray to the image. Afterall, true line art contains only pure black and pure white,

with no shades of gray. By converting your image to Bitmapmode in the end, youll guarantee that it wont be contami-

nated with grays. Shades of gray are reproduced using apattern of black circles, known as a halftone, which makesthe lines of your image appear fuzzy ( Figure s 1.3 and 1.4).

Figure 1.3 A Grayscale mode image of line art. Figure 1.4 Magnified version of

grayscale line art as reproduced on alaser printer.


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When scanning a line art image foronscreen display (for multimedia,the Web, and so on), the imagewill usually look better if you leaveit in Grayscale mode. I know, Iknow, that really isnt true line art,but it will look better onscreen.

Why? Because the pixels that makeup your screen are quite large(between 72 and 96ppi), so itseasy to see the jagged edges of thepixels that make up your image. Byincluding shades of gray, the edgesof the image will fade out and havea smoother look. When scanningfor onscreen use, use a resolutionsetting of 85.

Avoiding the Jaggies

The most common complaint I hear about line art is that it has jagged edges ( Figure 1.5). This happens when thepixels in the image are so large that you can easily seethem when the image is printed. Thankfully, avoiding the

jaggies is the easiest part of dealing with line art.

Resolution Is the Key

Photoshop gives users the ability to try a lot of wild things with images. But the one thing all users have in commonis the desire to get the highest quality possible. And when

youre working with pure black-and-white line art, that means youll want each pixel in your image to be the exact same size as the smallest dot your printer can reproduce.

The size of the pixels in your document is determinedby the resolution setting of your le. This is measured inpixels per inch (ppi). The resolution of your printer dic-tates the smallest dot it can reproduce. This is measured indots per inch (dpi). Youll want to nd out the resolutionof your printer and use that setting when scanning yourimage. This makes your pixels the same size as the smallest dot your printer can reproduce, thus giving you the best possible results.

Most people think higher settings produce better results,

but thats not necessarily the case. If your end result isprinted on a restaurant receipt printer, and you feed it animage with 300 pixels per inch, theres no way it can print dots that small. So it must distill the image and discard theextra informationand thats when your image will suffer.

Youre much better off using the correct resolution settingin the rst place.

Printing companies and service bureaus have expensiveoutput devices that offer resolutions of at least 2,540dots per inch. Ive found that les with resolutions above

1,200ppi dont seem to produce better detail; they just give you huge le sizes and therefore slow down your computer.Figure s 1.6 to 1.11 show the effect of resolution on le sizeand quality.

Figure 1.5 Jaggy line art.


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Figure 1.6 Resolution: 72ppi. Filesize: 22KB.





Figure 1.11 Resolution: 1,200ppi. Filesize: 93KB.

Photoshop Can Fake It

If your scanner is not capable of using a resolution settingas high as you need, you can have Photoshop increase theresolution of the image and add the extra information

your scanner couldnt deliver. To do this, scan with the

highest resolution setting available, and then chooseImage > Image Size. Select the Resample Image check box,set the pop-up menu to Bicubic (thats the kind of mathPhotoshop will use to add information to your image),type the resolution of your printer in the Resolution eld,and then click OK. Remember, your image must be inGrayscale mode; otherwise, this step will not improveimage quality. This step is unique to line art images; if you

were to increase the resolution of a photographic-quality image, the result would appear blurry. In the case of lineart, the extra information will not harm the image, because

were going to convert it to a pure black-and-white bitmap, which is incapable of appearing blurry.

Line art file sizes will vary depend-ing on which file format is used.

The preceding images were savedas TIFF files with LZW compressionturned on. LZW compression isideal for images that contain largeareas of solid color. The 1,200ppiimage above would have been410KB if LZW compression had notbeen used.


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Straightening the Image

If the image youve scanned needs to be straightened, you can use the Measure tool (it looks like a ruler and isgrouped with the Eyedropper tool). Draw a line acrossan area that should be perfectly vertical or horizontal. If

theres more than one area of the image that should bestraightened, you can click the middle of the measurement line and drag it around your screen to make sure it match-es all the affected areas. If you need to adjust the angle of the measurement line, just drag one of its ends.

When youre certain the line is at the proper angle, checkto make sure the background color is set to white and thenchoose Image > Rotate Canvas > Arbitrary. Photoshop hasa great feature that automatically calculates how much theimage needs to be rotated based on the line you drew, soall you have to do is click OK ( Figure 1.12). Once youredone, you can get rid of the measurement line by click-ing the Clear button in the Options bar at the top of yourscreen.

Improving Definition

When you convert an image to Bitmap mode (which welldo at the end of this chapter), any areas that are darkerthan 50% gray will become pure black. This usually causes

detail in the darkest, most densely packed areas to clogup and become a black blob. You can prevent this fromhappening by sharpening the image. Sharpening will addmore contrast to those densely packed areas and producebetter detail. However, before you sharpen an image, youll

want to take a snapshot of the unsharpened image so youcan use it later to enhance the result.

Taking a Snapshot

Choose New Snapshot from the side menu of the History

palette to record what the image looks like before yousharpen it. Name the snapshot something like Unsharp

Version so you can remember what it contains. Thesnapshot you create will appear near the top of the History palette ( Figure 1.13). Click the column just to the left of the snapshot thumbnail icon to tell Photoshop to use this

version of the image when using the History brush.

Straighten a scan while its still inGrayscale mode. If your image is inBitmap mode, it can be rotated onlyin 90-degree increments.

Whenever possible, avoid straight-ening scans in other softwareprograms, such as your page-layoutprogram. If scans are straightenedin other programs, the screen re-draw will take longer and printingtime will increase. Also, the qualityof the art will suffer, and youll nothave a true image preview.

When you scan grayscale imagesthat have already been printedusing a halftone screen, youll

often get an unwanted repetitivepattern. You might get a betterresult by scanning the preprintedimage as line art (even though its agrayscale photo). This method willtry to capture the halftone look in-stead of converting the image intoa grayscale file. Using the line arttechnique described in this chapter,you can scan grayscale images thatwere printed with a halftone screenof 85 lines per inch or below. If animage was printed with a halftonescreen above 85 lines per inch,the image should be scanned as anormal grayscale image instead of using the line art technique.

Figure 1.12 Photoshop looks at theline you drew and automatically calcu-lates the rotation amount needed and

puts it in the dialog box.


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If you need to have a transparent background for the web,press Option-Command-~ (Mac) or Alt-Ctrl-~ (Windows)to select the background of the image. (Youll use the tildekey, which is located to the left of the number 1 key.) Next,choose Select > Inverse to select the line art. Then createa new layer, choose Edit > Fill and ll the layer with black,and nally drag the original layer to the trash at the bot-tom of the Layers palette.

Sharpening the Image

Now that youve created a snapshot version of the image,its safe to proceed with the sharpening process. Double-click the Zoom tool in the Tools palette to view the imageat 100% magnication; otherwise, the onscreen preview of the sharpening lter will not be accurate. Choose Filter >Sharpen > Unsharp Mask, and set the amount to 500, theradius to 1.2, and the threshold to 2. This is usually a goodstarting point because it will make the detail in the darkareas more dened.

Now adjust the Radius setting until any tiny elements(which usually come in as light shades of gray) turn dark.

Youre really looking for a balance between good shadowdetail and dark tiny elements. Radius settings between .5and 5 usually produce the best results ( Figure 1.14).

A Threshold setting of 0 will sharpen all shades in the im-age, including the lightest grays. High threshold settings

will sharpen only the darker thick lines in the image. Iusually keep the Threshold setting at 2, unless any papertexture starts to show up. If you notice that the paper tex-ture is being exaggerated, increase the Threshold settinguntil the paper smoothes out again, and then readjust theRadius setting to maintain that shadow/tiny-detail balanceI mentioned earlier.

Converting to Line Art

When you print an image that contains shades of gray, your printer uses a halftone screen, which prevents yourgrayscale image from having crisp edges. In order for youto get nice, crisp edges, the image must contain only pureblack and pure whitethats true line art. So, how do youget there?

Figure 1.13 After creating a newsnapshot, click to the left of thesnapshot thumbnail image to set theHistory brush to that snapshot.

You can also click on the cameraicon at the bottom of the Historypalette to create a snapshot. Holdthe Option key (Mac) or Alt key(Windows) if youd like to beprompted for a name.

The Unsharp Mask filter is used herebecause its the only sharpeningfilter that gives you enough controlover the end result. The otherfilters deliver a more generic resultbecause there are no user-defined

settings involved.


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Figure 1.14 The Radius setting controls how much shadow detail will appear.

Adding a Threshold Adjustment Layer

You can use the Threshold command to rid the image of all shades of gray, leaving only pure black and pure white.By applying Threshold on an adjustment layer instead of directly to the image, youll be able to easily make changesafter the image is black and white. To achieve an accurate

There is no need to apply a Thresh-old layer if your end result will beused onscreen for the Internet ormultimedia, but you might need toenhance the contrast of the imageby choosing Image > Adjustments> Levels. Move the upper-leftslider until the lines in your imagebecome completely black, and thenmove the upper-left slider until thebackground is completely white. If youve done that, then you can stopright here and save your image inthe GIF file format.


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preview, you must view the image at 100% magnication.Double-click the Zoom tool in the Tools palette to quickly zoom to 100%. Create a new Threshold adjustment layerby choosing Layer > New Adjustment Layer > Threshold.

Adjust the slider until the lines in the image have thedesired thickness and detail. You can compare the black-and-white result to the grayscale version of the image by turning the Preview option off and on.

The Threshold level forces anything darker than thethreshold number to black and anything lighter to white(Figure s 1.15 to 1.20). Refer to the table in Chapter 5,Optimizing Grayscale Images, to see what the thresholdnumbers mean.

Figure s 1.21 to 1.23 show the quality improvement that is possible by scanning in Grayscale instead of Line Art

mode. Even more detail could be brought out of Figure 1.23 by using the enhancement techniques that were ap-plied to Figure 1.24 .

Figure 1.15 The lines appear to bebreaking up.

Figure 1.16 The Threshold setting istoo low.

Figure 1.17 This image shows goodhighlight detail without plugging upthe shadow detail.

Figure 1.18 Proper Threshold setting.

Figure 1.19 This image has noshadow detail and the lines are toothick.

Figure 1.20 The Threshold setting istoo high.


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Figure 1.21 Raw line art scan (sameas scanning in Grayscale mode andusing the default Threshold setting).File size: 448KB.

Figure 1.22 Raw grayscale scan (linesare not crisp, and the file size is verylarge). File size: 7.9MB.

Figure 1.23 Grayscale scan withsharpening and a proper Thresholdsetting (shows good shadow detail).File size: 584KB.


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Refining Areas

To retain additional detail, you must enhance the grayscaleimage thats below the adjustment layer. To do so, click thename of the layer that contains the original image. Thereare many ways to enhance the image, including the follow-

ing. (Refer to Figure 1.24 for examples of these settings.)

You can change the current brushsize at any time by pressing [ or ]

(square brackets).

Figure 1.24 Refining the image.

The History brush usingMultiply blending mode.

The History brush usingLighten blending mode.

The Dodge tool with 100%exposure setting.

The History brush usingScreen blending mode at45% opacity.


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Figure 1.25 Unrefined image. Figure 1.26 Result of applying theDespeckle filter.

Figure 1.27 Result of applying theMedian filter.

. Increase shadow detail: Brush across the image with theSharpen tool to bring out detail in shadow areas.

. Fix broken lines: Brush across the image with the Burntool (with the Range option set to Shadows) to cleanup broken lines or to make lines thicker. If the Burn

tool doesnt change the image enough, use the History brush with the Mode option set to Multiply or Darkento increase the line thickness. Lower the Opacity settingif the changes are too extreme.

. Reduce line thickness: Brush across the image with theDodge tool (with the Range option set to Highlightsor Midtones) to reduce the thickness of lines. If theDodge tool doesnt change the image enough, use theHistory brush with the Mode option set to Screen orLighten to make the lines thinner. Lower the Opacity

setting if the changes are too extreme. If the Dodge and Burn tools dont change the image

enough, use the History brush with the Mode optionset to Hard Light to make lines thinner. Lower theOpacity setting if the changes are too extreme.

. Remove paper texture: Choose either Despeckle orMedian from the Filter > Noise menu ( Figures 1.25 to 1.27).


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Figure 1.29 The Trim command willdiscard any extra space in your image.

Figure 1.30 The Bitmap dialog box.

You have to perform the trimmingstep when the image is still inGrayscale mode because the Trimcommand does not work on imagesthat are in Bitmap mode.

In Bitmap mode, the image cancontain only pure black and purewhite; therefore, the file size ismuch smaller than for a grayscaleimage. In fact, grayscale imagesare eight times as large as bitmapimages.

Figure 1.28 This image is split intothirds vertically. The middle is theoriginal, the top is after applying

Minimum, and the bottom is afterapplying Maximum.

. Control text thickness: If youre scanning text at largepoint sizes, you can make the text thicker by choosingFilter > Other > Minimum, or make it thinner by choos-ing Filter > Other > Maximum. If the adjectives used inthese menu options seem contrary to common sense,

well, they are. Just remember to apply reverse logic when dealing with text thickness ( Figure 1.28 ).

Minimizing File Size

Nobody likes dealing with big, bloated les. Theyre greedy resource hogs that slow down your system and wreak havocon your ability to work quickly and efciently. Any extra

white space around the image is a le-fattening waste be-cause its not necessary for printing the image. One way tosimplify the image is to choose Flatten Image from the sidemenu of the Layers palette, and then use the Eraser tool toclean up any stray pixels in the white area surrounding theimage. Finally, to discard any extra space, choose Image >Trim, turn on all the check boxes at the bottom, and thenchoose whichever top choice would make Photoshop nda white pixel ( Figure 1.29).

Converting to Bitmap

Your image is now pure black and white, but the le itself is still in Grayscale mode. You can click the eyeball iconnext to the adjustment layer to toggle it off and on andsee that its being applied to a grayscale image. The im-age must be converted to Bitmap mode to save disk spaceand to make sure that any nal editing doesnt produceunwanted shades of gray. Convert the image from Gray-scale to Bitmap by choosing Image > Mode > Bitmap. Thisbrings up the Bitmap dialog box ( Figure 1.30), which is

where you can change the resolution of your image. If youfollowed the steps mentioned in the Avoiding the Jaggies

section at the beginning of this chapter, then the resolu-tion of your image should be just right. If thats the case,then make sure the input and output resolution numbersmatch, so Photoshop doesnt mess with the Resolution set-ting, and then click OK.


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Choosing a File Format

If your image is destined to be printed, then youll want touse the EPS or TIFF le format. The EPS le format allows

you to specify whether the white areas should be solid ortransparent ( Figure 1.31).

Line art images that are destined for the web should besaved in the GIF le format.

Closing Thoughts

Lately Ive been noticing that a lot of the line art out thereis inferior to what I used to see only a few years ago. Checkit out for yourself! Pick up any magazine (even the high-end ones sometimes have this problem) and look throughit for line art images. If your experience is anything like

mine, youll probably see some really mediocre stuffedges are jagged, lines are broken up, and patterns lookclogged. My theory is that people stopped sending out forline art scans and started performing them in-house.

Thats ne, but only if youre not sacricing quality forconvenience. After reading this chapter, I hope youllagree with me that you can have both. As long as you knowhow to get a good scan that captures the right amount of detail, and then know how to enhance the scanned imagein Photoshop, theres no reason why you cant end up withexquisite line art.

And as a side note, I want you to know that just because you can achieve high-quality results using these techniquesdoesnt mean you will want to use them for every line art scan. I occasionally have to scan dozens of images for asingle project. In that case, I might decide that speed ismore important than quality and just scan in Line Art mode to begin with. But if Im scanning my own signature,a high-quality etching, or a logo Ill be using over and overagain, then I will denitely spend the extra time to get ahigh-quality result.

If you resize an image thats alreadyin Bitmap mode, the individual pix-els in the image become large blacksquares. To maintain good quality,convert the image to Grayscalemode and then use the GaussianBlur filter with a setting just high

enough to introduce shades of gray(Figure 1.32). Now you can usethe techniques listed in this chapterto enhance the image and convertit back to Bitmap mode.

Figure 1.31 The EPS Optionsdialog box.

Figure 1.32 The Gaussian Blurdialog box.

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Bonus CH-01 Line Art

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