NOW YOU SEE IT, NOW YOU DON'T
By Deborah J. Cook

Graphic"How do I get rid of the white background?" is one of the most frequently asked questions I come across from people looking for graphics and DTP help, because, let's face it, nearly everyone reading this has been handed camera-ready art (or worse) as your client's only means of providing you their logo. Of course, you scan it. Then you're left with a bitmap, and even more fun the bitmap's background.

Because bitmaps are pixel-based files (each PIcture ELement is assigned a coordinate and color value), the background is always there. So, while you can't really remove the background pixels from a bitmap file, the trick to hiding that pixel information is in how you tell the receiving application to treat those pixels either before you've imported it or with some manipulation after the image is placed.

With each successive version of CorelDraw and Photo-Paint, more "tricks" to hide pixels were introduced and improved upon, and removing those pesky backgrounds keeps getting easier.

Version 5
Fig1
Although you can import transparent B/W bitmaps and even change the foreground and background colors by left- and right-clicking the palette, true transparency functions for color bitmaps were still on the horizon when CorelDraw and Photo-Paint 5 were released. If you are looking to create those nifty transparent GIFs (89a format) for your Webpage, you'll either have to upgrade to Photo-Paint 6/7/8 (and Win95/NT) or use one of the many sharewa Fig2re bitmap editors available for download. But if you are taking your CDRs to print, there is a version 5 trick or two for you.

Start by Importing your bitmap into Core Fig3lDraw (Alt+F,I) and immediately deselect it so you won't activate the Auto-Trace tool with the next step. Using the Bezier tool (F5), begin creating a Powerclip Container for your image. Don't worry about accuracy at this point; just get the basic shape drawn. You can go back later with the Node Edit rollup (double-click Shape tool) and your pointer to reshape the Container.  (See Figures 13. The Powerclip Container is shown in cyan for clarity.) Remember, even if your bitmap's background is not a contiguous area, you can still Powerclip (Alt+C, W, P) it by Combining (Ctrl+L) several shapes into one Container.

You can also use Photo-Paint to create a simulated transparent background from a Mask that encloses that part of the image you want to keep. Save As an EPS file, and Import it into Draw using the Postscript (editable) EPS filter. The object will be imported into Draw as a curve with a full-color bitmap fill, w Fig4hich means that if you try to resize it, you'll get a tiled fill. (Fig. 4.) To avoid tiling, select the object and open the Fill rollup (Shift+F6). Click on Update From and select the object again. Click on Edit and enable Scale Pattern With Object, and click Apply.

Version 6
Fig5
With the release of CorelDraw and Photo-Paint 6 came much improved bitmap handling. Seemingly by magic, you can import a bitmap into Draw and then watch the background (and other unwanted colors) vanish! With the bitmap selected, open the Bitmap Color Mask rollup (Effects|Bitmap Color Mask),  and click on the Eyedropper tool. (Fig. 5.) Use the Eyedropper to select the colors from your image to be hidden. Use the slider to adjust the Tolerance for similarly colored pixels. Because all pixels of a p Fig6articular color or range will be hidden by the Bitmap Color Mask, you might want to first use Photo-Paint to fill those pixels with a discrete color and then choose it with the Bitmap Color Mask Eyedropper. (Fig. 6.) The Bitmap Color Mask does not work with B/W bitmaps, although you can still assign foreground and background color with the Fill and Outline tools.

CorelDraw allows you to use the Shape tool (F10) to crop imported bitmaps on the fly, but beginning with version 6, you are n Fig7ot limited to "straight-edge" crops. You can add and subtract nodes; convert the paths to curves; and pull, push and reshape to your heart's content. With a bit of creativity and perseverence, backgrounds can be cropped from view. (Fig. 7.)

Alpha channels in Photo-Paint are yet another option in version 6. Mask the background (or other areas you wish to hide) and then Invert the mask (Alt+K, I) so that the area to remain visible is enclosed by the selection. Open the Channels rollup (Ctrl+F9) and click on the Channel from Mask button. Save the image as a TIF. Upon import to CorelDraw 6, the alpha channel will "clip" the background.

But wait, that' Fig8s not all Photo-Paint 6 creates Clipping Paths! Mask your image as above (or use the Path Node Edit tool to create a path from scratch), and with the Tool Settings rollup open (Ctrl+F8), select the Path Node Edit tool from the Toolbox. Click the Path from Mask button and save the file as an EPS, checking the option to Save Image Enclosed by Path. Import your EPS file into Draw using the PS Interpreted filter and perform any necessary "clean up" to the clipping path with the Shape tool (F10). (See Fig. 8, with bitmap hidden to emphasize Path.)

Version 7 and Beyond Fig9

You may already be thinking all of this stuff so far is pretty neat, but Corel just won't cry "uncle." Although you could create objects and layers in earlier versions of Photo-Paint, and even preserve them with the CPT format, now you can import a layered CPT (or PSD) file into CorelDraw 7/8 Fig10and Ungroup (Ctrl+U) to edit the layers! (See Figs. 910.) Don't like the white background in your bitmap? Hit the Delete key! Really want those two objects a teensy bit closer together?  Ungroup 'em and move 'em around! It slices! It dices!  Uh-oh, I've been watching too many infomercials.

CorelDraw 7/8 also includes much of Photo-Paint's functionality right inside the Draw module. This means for those of you still wary of bitmap editors, you never even have to leave the comfort of your Draw home to create transparent bitmaps from your vectors. Create your artwork, and from the Bitmap menu select Convert to Bitmap). Choose your color depth and resolution and check Transparent Background. (See Fig. 11.) If you are planning to use Fig11 some of the Effects filters included in Draw 7's in-place bitmap editing, you should enclose your object(s) within a no fill, no outline box to create a "cushion" of workspace for the Effect. Draw 8 has an Auto-Inflate Bitmap option.

Note: The transparency option for Draw's Convert to Bitmap function will only affect white backgrounds; there is no option to choose another color for transparency.


Internet Transparency

It's near impossible these days to write a computer-related article and not mention the Internet and this one's no exception. Transparent GIFs are a hot item for homepages and Web design. How do I create 'em, you ask? Well, if you're using version 5, you can't at least not directly. As mentioned earlier, you'll have to upgrade or seek out another bitmap editor to resave your GIF87a files to the GIF89a format.

With Photo-Paint 6, GIF transparency became an option. Although you are still somewhat limited to using the Eyedropper tool to che Fig12ck the Index number of the area to be transparent and entering that Index number in the dialog box that comes up when you save to the GIF format. (Fig. 12.) Note that the GIF format will not be available in the Save As file type list unless your image is 8-bit/paletted (Image/Convert), and the transparency options will be grayed out until you choose the 89a format.

You have more options when saving GIF files from Photo-Paint 7/8. And if you try to Save a non-paletted image to the GIF format, a warning will pop up reminding you of  the error of your ways and begging you to repent. (Okay, so I added in that last bit about repentance!) As in version 6, you can note the Index value of Fig13 the area to be transparent with the Eyedropper tool and enter that number in the GIF89a options dialog box. But with version 7, you can use your pointer to click on the thumbnail itself to choose a color for transparency or you can pick a color from the image's palette box. You can now also set the transparency from the image's Mask. This is especially handy if you'd like more than one color to be transparent, or if you only want certain areas within the same color to be transparent. When you choose Transparency from Masked Area, the Select Color box becomes active. This option allows you to set the overlay color (as shown in yellow in Fig. 13) on the thumbnail for the representation of transparent areas, and does not reflect the value of the actual transparent color(s).  With version 8, Photo-Paint GIF exports are improved, with a dialog box allowing many more export options and a preview so you can view before and after versions of your paletted image.

Note:  When Importing transparent GIFs into Draw 7/8, the transparency will not be retained; use the Bitmap Color Mask to redefine transparent areas.

So, now armed with all of these options, Go Forth and Be Invisible!


Debbie Cook is a self-employed graphic artist in Brandon, Florida. She is a Corel Certified Instructor, and also provides technical support for Corel Corporation as a C-TECH Support Partner on Corel's Compuserve forum and newsgroups.
 

© Copyright 1997, 1998 by Deborah J. Cook