When a reader wrote to Images asking for help with multi-colour blending for a logo, Erich Campbell was only too happy to help.
Gradient blending is a greatly misunderstood technique. Automatic blending tools may increase the spacing between each fill line gradually from one side of an element to the other, or even layer a second colour with the same settings in reverse of the original, but the stitched result can suffer from uneven coverage and lacks the smoothness that is the defining quality of a gradient. Rather than rely on automation, you can create smooth blends using basic tools provided you’re willing to do the work yourself. With careful planning, you can achieve a gradient with smooth transitions and even densities for the surface quality and pliable hand that customers demand.
The first step is to know your medium. You can’t blend as you might with ink, nor can you produce nigh-imperceptible halftone dots to trick the eye into seeing seamless transitions – each stitch is an unalterably coloured physical object. What you can do is place and arrange each stitch in relation to its neighbours, and to strike a balance, using as few thread colours as possible for production friendliness and as many as needed to reasonably represent your art. Careful placement of your stitches can also help to hint at thread colours you can’t afford to use, and the viewers’ eyes will also blend and perceive a wider range of colours than those that are actually present.
Analysing your art
Imagine that lines of stitching are painted pencils. A full-density ‘fill’ is a tight, single layer entirely covering the surface below. If you had red, orange, and yellow pencils and wanted to lay out a smooth transition from red to yellow, you might start with solid areas of the three colours. Seeing solid bands, you might divide the space between areas left solid, interchanging the pencils to make a smoother transition. You’d choose how many pencils of each colour to place in each area so that as you move from one colour to another, each section has more of the colour you are moving towards and less of the colour you are leaving behind. It sounds complicated, but is relatively simple. If you divided the area between solid colours into three sections, you could express the way you fill each section in percentages. The first would have 75% of the first colour and 25% of the second, the next 50% of each, and the third 25% of the first colour and 75% of the next, leading into the 100% coverage section in the next colour, switching between colours along the way so that they are spaced as evenly as possible in each area. This is almost exactly what you will do in thread. Here’s how…
1. First, find the angle of the gradient. In blending, all stitching must follow one angle so that the lines can be interspersed and ‘fall’ into the colours stitched earlier in the sequence, matching the angle of coloured sections in the original.
2. Next, select key thread colours from the gradient. When you are given a lossy raster image (like JPGs), you’ll see a certain amount of blending or dithering in the art. The pure bands of colour in a gradient – those without dots from other colours – hint at potential thread colours, though you may choose colours that compromise between these bands to reduce your colour count. Attempt to keep thread colours as close to each other in tone as possible: the more contrast between neighbouring colours, the less smooth the blend appears.
3. Finally, partition the blend area. As noticed in selecting thread colours, you can often see banding in a dithered blend. By marking these transitions and calculating the number of ‘sections’ you’ll need to blend, you can establish the areas of your fill. If the gradient is uniform and presents an even curve rather than stepped, short transitions, you can draw evenly spaced lines across the area. Draw these guidelines at the angle of the gradient and in a colour that highly contrasts with your design area and lock them. They will help guide you in creating and placing your blend stitching segments.
With your art prepared, you can use one of two effective methods to create a smooth gradient; manual point-to-point digitising or overlapping light density fills.
In this method, you plot stitches one at a time for fine-grained control of the blend (see figure 1). You are not bound by evenly-spaced fills, but can vary the density throughout the process, passing through ratios between the aforementioned 25% steps for smoother transitions (see figure 2). Though you will pre-plan segments, accounting for the ratio of one colour to the next, you are free to adjust by eye. You can plot each colour in a single pass, varying spacing from section to section and leaving open lines/areas for the next colour in the sequence (see figure 3). This single pass avoids the larger traveling stitches and overlaps that the low-density fill method (se below) creates at the edge of the blend area. I create a standard full-density fill to use as a guide, locking it on a layer just above my art (this fill is deleted once the digitising is complete). With stitch penetration points visible, I use a combination of guidelines, original art and the locked fill to direct my digitising. I place each stitch, following the set angle, placement and penetrations from the standard fill while skipping lines to match my ratios (25% coverage means one of every four lines of the guide fill are covered, 50% covers every other line, etc.), filling in the purposefully empty lines from one pass with the next colour in the sequence. Though this throwback to the earliest days of digitising may not be cost-effective for large areas or small-quantity runs, it creates a smooth result (see figure 7).
Overlapping light density fills
With the overlapping light density fills method, you use multiple passes of light-density fill to work up to full coverage, overlapping areas in subsequent colours to achieve the percentages I described in my earlier example (see figure 9). You lay down a basic underlay as needed in a medium tone from the blend and start filling, allowing each colour’s fills to fall into the earlier light-density fills of the previous colour. When drawing lines to mark your 25% density segments, create one segment for each solid thread colour and allow for three segments between the solid segments. This means that the first fill (for a 0.4mm full density, a fill spaced at 1.6mm) spans the entire area of one colour, after which a smaller fill with the same settings is placed atop the first, offset by the width of a thread. This smaller fill creates an area of 50% density coverage and leaves some of the original fill exposed at 25% density. This continues until the last 25% coverage fill brings the solid colour segment to 100% density and the fills surrounding it step down 25% in each section until the next ‘pure’ colour segment (see figures 10 and 11). With this method, you may have to alter the stitch penetration patterns or utilise user-defined stitch points to arrive at a smooth texture; when penetrations align, it can cause the appearance of a stepped or brick-like surface pattern.
No matter how you digitise your gradients, the key elements are the same: observe your art, carefully select your colours, and build densities until you hit full coverage, making room for each colour you layer into your design. Don’t get me wrong; for hints of blending or shading on most designs, you may elect to suffer higher densities or subtle stiffness, layering light shading atop a complete fill. That method often makes the most sense artistically and for profitable production, but when you are staring at a four or five colour complete gradient on a light garment, you’ll be glad you know how to plan and execute these balanced blends.
Erich Campbell is an award-winning digitiser, embroidery columnist and educator, with 18 years’ experience both in production and the management of e-commerce properties. He is the partner relationship manager for DecoNetwork in the USA.