Never leave a piece of photorealistic artwork untouched.
Although Adobe Photoshop is the defacto standard raster/pixel based program that the world uses for pixel based images – many of the tools found in Photoshop are also found in Corel Draw and Corel Photopaint. In fact, years ago Corel made a great move when they built in more pixel/raster support for images. You often think of Corel as only being used for vector/cartoon type of artwork but under the hood it is very powerful and can do wonders with low quality artwork. I first wrote this article for Photoshop but had requests to modify it for Corel users. Here it is.
image. Otherwise you could be working on a very small file and not know it. Go to Bitmaps/Resample. (Figure 1) The resolution should be 200 dpi or higher in pixels per Inch. For high quality images, 300 dpi is preferred. For T-Shirt graphics that can be more forgiving you can work at or near 200dpi – at the final print size. The physical size should be the final print size.
As you can see in Figure 1 this is not the case in our sample image. It is only 62dpi and about 7” x 5” physical size. At 62dpi it will be very pixilated. But wait… you say the file looks good on the monitor. If you wonder what the file really looks like zoom in on it. Wow! The inset picture in Figure 2 shows a zoom of the face. From a distance it looks great. You assumed it was OK but when you zoom in you see it is not OK. And you wonder why the file is soft with no detail when you print it.
Upsampling/Resampling is a partial solution. OK, you can only do so much with bad artwork. But,
The Tone Curve is a very powerful tool. It lets you adjust specific tonal areas from the lightest "highlights" to the darkest "shadows." By placing your cursor in the middle of the curve "midtones" and dragging the mouse up or down, you can lighten and darken the medium or midtones in an image. By clicking on the very top corner and dragging the mouse in, you can make the highlights lighter. Play around with the Tone Curve and see what happens. An good curve for flat images is a slight “S” where you lighten the highlight 25% area and darken the 75% shadow area. You have to look hard to see the “S” in Figure 5 but notice the difference in the design. In some cases using the Tone Curve is better than boosting saturation for bringing out colors.
Typcially, an image can be made sharper. Even if the file came from an agency or large licensed job, don't assume that their artist knew your needs. Images that are printed, not only can get darker but they get softer. Especially if you are going to screen print them. You MUST make them as sharp as possible.
Go to Bitmaps/Sharpen/Unsharp Masking. Don't let the "unsharp" term fool you. This term came from the old process camera days and basically means is only sharpens areas of high contrast. It sharpens but keeps it less apparent that you have sharpened the image.
Set the Amount slider to 200, the Radius to 1 pixel and the Threshold to 8. How does the image look? If you can't see much difference, move the Amount slider higher. Go all the way to 500% if you need. Don't get the image too grainy. You need all the help you can get with images so don’t be shy about improving the sharpness. See Figure 6.
If you do nothing but these changes/fixes you will be home free to getting the best possible print possible – not matter what your printing technique is.