I have written extensively on mosaics and mazes, color separations required for drawing their motifs, and visualizing the resulting patterns while planning slip stitch or tuck repeats. A recent exchange with a knitting friend, Tanya Cunningham, brought up her idea of using Gimp to investigate the potential of self-drawn tuck patterns becoming pleasing mazes or mosaic designs in color. Tanya has worked extensively with img2track, can be found in the FB group and Ravelry. It had not occurred to me to reverse engineer designs for this purpose. Tanya uses Gimp in a different way than I do, I am hoping she will share her process for this purpose when documented.
I have grown comfortable and fast with the combined use of Numbers and Gimp to achieve what I desire in terms of color separations. At the moment, on the assumption that estimating the overall shape is the goal, a black and white processed rendering may be a sufficient representation of the result.
Punchcard books are a great source of “safe” tuck designs. The best are those that have columns one stitch wide by 2 rows high. They are also more interesting if there are areas of solid black. Patterns from publications intended for use on electronics are often color reversed to start with in order to minimize drawing pixels or to make the design easier to read and will have lots of blank areas. Punchcard users would need to punch the ground as opposed to the design, electronic users can achieve the goal by the flick of a switch or a quick software command. For my first series of steps and methods, I am using the repeat that appeared as a knit using different settings in the post on mazes and mosaics from universal patterns.
Presented on the left, the repeat would be suitable only for thread lace or FI with very long floats. Color reverse allows one to use it for tuck and slip stitch, whether in one color or with color changes every 2 rows. 
The color separation to approximate the result with color changes begins with the same process as that used for designing mosaics. Once the image is rendered as a correct B/W png with no apparent errors, it is copied and pasted on a larger canvas, the mode converted back to RGB. The red cells make it easier to keep track of rows that need to be color inverted. Using the shift key and rectangle tool, multiple pairs of rows can be selected sequentially and color inverted. Beginning the selection with the very edge of the black squares on the left does not interfere with changing the color of the extra columns on the left side of the design. If pixels are added accidentally drawn in any of the 4 extra columns on the left, they can easily be removed when the completed conversion is cropped to selection for the final repeat. 
The completed color separation can then be bucket filled to match imagined colors
Tiling the repeats to imagine the final knit presents the problem that results from working on a square grid and comparing the results to a knit, which usually produces a rectangular one. The representation for the linear patterns produced on the knit side of the piece cannot factor in some of the added distortions created by the stitch type used. I process my images in Pages or Numbers, depending on which document contains my most recent work and happens to be open. It is also possible to perform the final rescale in Gimp. Most knits approach a 4:3 ratio, with gauge variants in highly textured fabrics. To preserve a clean design, tile and save the original, screengrab the resulting image, load it in Gimp, and rescale. Repeat the motif for the same number in both height and width when tiling it. 
The colored versions before and after scaling, compared with the slip stitch swatch. 
It is possible to produce a rectangular grid to start with on which to draw in Gimp, but the larger canvas size occupies a significantly larger space on the screen, complicating the process. For small designs, however, that may be an option to give one the sense of aspect ratio for the design in the final knit ie in representational FI. To resize the grid in uneven proportions, the chain-link below the spacing values needs to be broken 
This repeat is designed for an electronic, requires color-reverse. Since it is 24 stitches wide and it may also be modified and used on a card. In this instance, the original marks for rows and stitches are single height. The image is processed, matching the original, rendered double-height, color reversed, and then alternate pairs of rows were color inverted to render the repeat used in the test swatch 
Once again, the possible change in scale is estimated. The repeat though only 24 stitches wide, is 92 rows high. On the left the repeat is shown as it appears on a square grid, to its right is the scaled 4:3 version, in a pixel count approximating the size of the swatch. It takes a bit of squinting to see the pattern more recognizable in the longer repeat in the larger tile 
The swatch was pressed, becoming wider than when first off the machine. It was knit using the slip stitch setting, could also be executed in tuck stitch, which would both widen and shorten the fabric and make the purl side more interesting. The software can provide a preview of the result far more quickly than knitting samples, but again, the previews are only approximations of the scale, and cannot show distortions to lines as one adds more texture.
Repeating the process starting with a diamond shape that as given is only suitable for thread lace or FI with problematic floats, 
and with a check tuck pattern that may change in aspect ratio considerably when knitted 
The proof of concept swatch, knit in tuck stitch, begins to show the distortion by the stitch formations, textures vs plain knit, easily seen at the top edge. The bind-off is around 2 gate pegs in order to allow enough stretch. 
Anyone familiar with either or both programs may find this a very quick way to visualize the scaling and moving of motifs within DIY designs and their possible outcomes prior to test knitting
with my color changer in this threading sequence throughout
where normally each color in each design row knits twice. Because selection occurs for pairs of rows, the first preselection row is from right to left. To decrease the backing rows, the ribber is set for birdseye. I prefer to have an end needle on each end on the ribber, keeping in mind that the total number of needles in use there needs to be even. The machine provides reminders as to which color should be knitting. My samples are knit using KCI on the top bed. Because the preselection happens twice, it is easy enough to knit in pattern from left to right, 
when the carriages have reached the right side, simply use a ribber comb to push all needles back to B. 
Speeding things up with color separation, beginning with the method that will have each color, each design row knitting twice. The repeat is 10 rows high, so it is expanded X6 to 10 by 60 rows. In the final result, the second row for each color in the separation is in turn erased. The red was added to make all 3 colors visible while working the separation, avoiding confusion with the white ground. The knittable result as usual is in a black and white png 
The img2track settings are for now for 2 color knitting, the prompts for the color changes are lost.
The ribber can also be set to knit every row, resulting in elongation on the knit side, while creating an interesting striper backing
Comparing this version to the birdseye backed one for repeat height 
Comparisons: HoP, pushing back needles to B, and color separation results. In the latter, the design is likely elongated in part due to a change in the distribution of thinner yarns to larger design areas with no tension adjustments 
a partial illustration of 
Text may be activated by choosing text in the image/ tools menu 
by clicking on the tool icon A in the toolbox 
or by using t as the keyboard shortcut, then clicking anywhere on the canvas.
At the top of the Text tool dialog, the current Text Size, 11 in above, is shown in either pixels or points. A pixel is the smallest component in a bitmap image, and all measures in pixels depend on the screen resolution. A point is a fixed value, one inch is the same as 72 points. Standard screen resolution is often 72 pixels per inch, in which case text in pixels will be the same size as text measured in points.
The choices listed at 
After the text is entered on the canvas, right-click on the inside of the text box to change text direction 
After the chosen text is placed change its mode from RGB to B/W indexed, then crop the image to your chosen size. Export.bmp, the result loaded into img2track and Ayab
The usual text alignment rules apply in text boxes as well, left to right 
Getting more control of the process: after the text tool is highlighted and clicking anywhere on your canvas two things appear automatically. The four little boxes represent the text box, which is dynamic by default and grows in size to accommodate typed text. Anytime you click on the canvas a new text box is created.
The spacing between the lines and between the letters may be adjusted as well. Clicking on the arrows to change the values here is one option, negative or positive numbers may be used 
or what appeared easier to me, the same may be done here 
Very small fonts are likely not to have any room for decreased spacing in the between letters in strings of text.
The “striped” repeat produces essentially the same fabric. The knit carriage may be set to slip in both directions when using it since the row of all punched holes or black pixels will knit every stitch on every needle selected while in the previous samples the cam button set to knit in one direction performed that function regardless of any markings on the design repeat. The ribber is set to knit in one direction, slip in the other. Reversing sides for cam button settings produces the same fabric 
The 
The repeat I chose is designated as suitable for the Garter Carriage. It is 24 stitches wide by 48 rows high, shown below as provided, charted in Gimp as .png for download, and tiled to help visualize how continuous repeats might line up. The image .png was downloaded with img2track to my 930, with a stretch factor of 1.0, retaining the original repeat size
The design is automatically flipped vertically, so it will appear as intended on the knit side of the fabric. Yarn colors may be placed in the color changer matching the order in the assigned color numbers to match the placements in the original image. The program automatically adjusts for the vertical stretch, which changes the aspect ratio of the shapes. On my 930 I received prompts on which color to change to prior to doing so, eliminating any confusion. With no such prompts generally one can tell which color was knit last because it will appear on top of the previously used one on the left of the knit. With a stretch factor of 1 selected in img2track, the image height was reduced by half. 
In the past, I have preferred to elongate the design prior to importing with plans for download rather than to rely on memory for changing settings either in the download program or in the machine itself in future uses of the same design. 
The same yarns, tension, the total number of carriage passes, and settings were used showing the difference in aspect ratio between single color per row knitting and the img2track built-in color separation. 
The width of both swatches is essentially identical.
The 930 will provide prompts for the next color to be selected by pushing the matching number button on the color changer, avoiding any confusion in terms of what should be picked up next. img2track will also flip the design horizontally automatically so the image will appear as originally drawn on the knit side. Images are loaded as single motifs, so the change in the selector needs to be made manually for an all-over pattern.
Obviously a success in terms of the single row for each color reducing elongation of the design shape. While knitting occurs using the same yarns, at the same tensions, there is a clear difference in the length of each stitch on the main bed and their appearance. The reverse. Checking the ribber carriage I noticed on the left side it was set to knit only, not to slip: OOPS! 
N is king, so the ribber set as shown is knitting every other needle when moving to the right, but even with lili buttons in use, it knits on every needle when moving back to the left. Every other needle on the ribber will then be knitting for 2 rows as a result. The more knitting on the ribber for each pair of rows, the longer the stitches on the opposite bed. The backing is an interesting variation (half) birdseye. The elongated stitches on the main bed show more of the backing in between their shapes, it is referred to as bleedthrough. In some instances, the result can make the knit surface resemble weaving and its appearance far less familiar in a surprising, pleasant way. Beauty is in the eye of the beholder.
The images could be replicated as given in a paint program, using only one color for the squares, but “should be reduced to black and white”. Attempting to import an indexed 2 color image drawn in a color other than BW may result in strange results. 
That said, if glitched knits are the goal, the above could work just fine. Curiously, here is the same process, using a different color, and a successful import. Checking again, I had forgotten to save the image after indexing it from RGB mode to 2 colors. 
Note to self: if you are determined to use a punchcard carriage on your electronic machine remember there is no KCII to cancel end needle selection!
Getting that first row to knit twice instead of a single time if that matters in your technique or is your preference:
pick up color 1 in yarn changer
If black and white repeats are already in your library, one may easily recycle them adding a third color. Here I did so with a repeat intended for a very different topic in future posts. The image was altered and tiled in Gimp for a repeat alignment test and is also shown imported into img2track for possible knitting. 
The image of the separation on the above right has not been proofed for accuracy. If it were, the next step would be to elongate it X 2 for color changes every 2 rows. One method is to elongate the original in a paint or photo processing program. The width is fixed (40), the height is scaled X 2. The resulting BW indexed image may be imported, using a 1.0 stretch factor, it remains unchanged. When I tried to elongate the unstretched image in img2track by 2.0 my first try failed. It turned out the reason was I had saved the import without first indexing it to 2 colors. With that corrected, the result matched the one from scaling X 2 in height in the paint program
Here the image is scaled properly for each color represented for a single row in height, and also scaled again for double-height for possible knitting in Gimp. The Gimp scaling failed to be accurate for me (second image from left) until I indexed the original to 4 colors as well instead of 3. The no color rows as we view them actually serve as a fourth color in the separations. Importing the proper size png into img2track for separation of 4 colors per row now gives results that make sense: note the daunting estimate for the total number of carriage passes for a single repeat height
If the ribber has knit on every needle by its return to the color changer and the machine is set to slip both ways with no needle selection on the main bed, the “no color” can be executed as an empty yarn holder in the color changer combined with no yarn in the feeder. The rows involved should simply not knit on the top bed, with no dropping of any of its stitches since no needles will have been selected thus coming forward with the yarn in the hooks and traveling behind the latches and in turn, slipping off the needles as a carriage with no yarn pushes the needles with now empty hooks back to B position.
Punchcard knitters may have the easiest knitting variable color sequences since cards may be visually marked up with colored pencils matching needed change locations and taking into account your eyes are a number of rows above the row being read by the card reader. This number depends on the machine’s brand and model.
A comparison of my repeat using a single LC and the Knitlabo pattern expansion including memo options for use with 2 lace carriages
Back to the original method used in the previous post where ribber settings are changed from knit to tuck <– –> every 2 rows along with color changes. I chose a design that would make it easy to identify the location of non-selected needles on the main bed in rows where the ribber will be set to tuck in both directions. The result is interesting, but the solid areas, narrower than the remaining knit, are in the opposite color to the dominant one on each side, the reverse of the inspiration fabric.
The single 14X84 png 
Each of the 2 colors tucks for 2 rows and in turn, knits for 2 rows alternately. Settings are changed manually as shown below after every 2 rows knit, following each color change on the left. 
Making things a little easier: the top bed may be programmed on any machine, including punchcard models to avoid cam button changes in the knit carriage every 2 rows. With the main bed set to tuck <– —> throughout, black squares will knit for 2 rows, white squares will tuck, also for 2 rows. The first preselection row is toward the color changer. When no needles are selected on the top bed (white squares) the top bed will tuck every needle, the ribber is set to knit. 
Proof of concept: blue yarn is used on rows where main bed needles are selected (black squares). The crossed stitches at the top right begin to represent an effort to create surface shapes or designs on the fabric. They are created by crossing stitches 1X1, making certain the stitch creating the “shape” is carried to the front side of the fabric, the opposite stitch crossed so it is facing the knitter. 
Another attempt at cabling, 1X1 and 2X2. That white line in the bottom image on the right was caused by the color changer picking up and knitting both colors for part of the row before I noticed it. I got rid of the “wrong” color from the feeder and continued on. The wider 2X2 cables require “special handling” and eyelets are formed on columns aside from them after transfers are made. 
The situation is different when working on single bed vertically striped fair isle designs. One of my ancient machine-knit demo FI swatches: 
The charted repeat on the left below when tiled shows the area of a patterning error, on the right with the missing blank rows added the problem is shown to be resolved, the repeat is now 24 X 84. 
A proof of concept swatch: 
Adding complexity, there is the possibility of 
Other related fabrics may be found in posts:
