Category: Color reductions and dithering

A ladder back dbj quest

The previous discussion on this topic: Ladderback double jacquard: backing variations
This backing technique has traditionally been used when the yarns are simply too thick to be worked in traditional dbj backing methods.
The majority of the needles will be knit on the main bed, so the tension should approximate that used for the same yarn worked in stocking stitch single bed.
The pattern will become a slip stitch one, with colors changed every two rows.
A FB Machine Knitting Group share led to a query on how this block type of ladder back might be duplicated on home knitting machines. My interpretation of the knit: the planned block repeat, in turn, needs to be color separated and scaled for use in dbj.
This chart was developed using Numbers:
A: each color in each row is represented only once
B: the same repeat in black and white
C: the repeat double length so that each color is changed every 2 rows
D: getting the pattern to shift for every other pair of blocks is actually achieved by knitting the last 2 rows and the first two rows of the next repeat using the same color for 4 consecutive rows.
If the repeat is downloaded and programmed to be 24 rows long, the reminder to knit with the same color again is easy, since the pattern will roll back to row 1 with a warning, in this case, not to change color. It is easy enough to alter the height of the repeat to use this particular reminder. The motif used in the swatches is 14 stitches wide by 24 stitches high  The machine set up: the main bed needles will need to continue to have weight evenly distributed on them, so the ribber comb placement needs to reflect that. The cast-on method can be one you prefer. I began with waste yarn, the ribber comb poked evenly through that, with the added use of ribber weights.
The pitch setting is for every needle rib.
End needle selection is used as in fair isle knitting to ensure that end stitches will be knit when either color is knit only on the top bed, resulting in the B feeder yarn being secured on the edge. If the end needle selection fails for any reason on the carriage side, push the needle forward manually.
The needle arrangement with red lines marking the location on the opposite bed.COR: the first pass is made toward the color changer
COL: every other group of 7 needles is preselected, set both carriages to slip in both directions, change color if preferred, and bring up ribber needles in between those selected on the top bed to D position as shown here, on both the pass to the right and the return pass to the left.   As the carriages make the pair of passes, floats will be created across the alternate group of 7 needles. Those floats will become secured as the next group of needles is selected and ribber stitches are brought up to form a line of knit stitches in the contrasting color in front of them.   The yarn used here is 2/20 wool, really too thin for this type of backing, but I wanted to test the repeat and the concept.   Using a 2/8 wool the result was optically the best, but I could not get any further than this without stitches jumping off needles in several places, regardless of tension adjustments Using yarns in weight in between the 2, knitting was smooth, the tension on the top bed was set at tight as possible, this is the appearance of the knit on the machine  Off the machine, the bleed-through from the floats created on the top bed on the knit side begins to remind one of knit weaving as does the purl side. Not the intended effect and fabric, but perhaps worth pursuing intentionally. 

Online Pattern generators, hacks, free KM manuals, and more

I welcome being contacted re any problem links
generators that require color changing every 2 rows using a color changer (or 2 carriages)
mazes on gridded output, easily adaptable to knit http://www.ludiculus.com/maker/mazes.html
more mazes  http://www.billsgames.com/mazegenerator/
maze pattern http://www.unikatissima.de/e/?page_id=2062 blog closed 
cellular automaton http://www.unikatissima.de/e/?page_id=2148 blog closed  
Some unikatissima blog content may be found here, but generators fail as they relied on Flash Player, now defunct 
other generators that can help with shaping garments, or some basic knit motif design
knitting pattern http://kpg.sourceforge.net
top-down circular raglan calculator http://kpg.sourceforge.net
Icelandic round yoke design does not work any longer in later version browsers, on Mac even with the installation of Silverlight, on Ravelry, it was noted the program does operate in internet explorer  http://knittingpatterns.is/#/Design
random square patterns http://www.unikatissima.de/e/?page_id=3638  blog closed
punchcard generator and how to use videos 
math calculators for knitting
free online manuals, magazines
machineknittingetc.com now https://mkmanuals.com/
hacking
a hacking history https://www.beautifulseams.com/2014/10/29/tricodeur-writeup/
only the intro is in German: a nearly hour-long presentation by Fabienne
another approach for Brother models KH”‘930, 940, 950i, and 970: http://daviworks.com/knitting/ and the associated group on Ravelry 
970 how to hack instructable 
for additional cumulative information, software compatibility and hardware specs see Claire Williams’ website
GitHubs
PatternUploader
color reductions/ conversions for large, nonrepetitive images Mac
online dither generators
https://ditherit.com 9 dithering types
https://app.dithermark.com  a huge range of possibilities
Hand knitting websites worth a browse:
https://www.knittingfool.com/Pages/Reference.aspx
pattern generators/ web design
open-source charting program http://sourceforge.net/projects/sconcho/
quick screenshot

1/21/2016: Online weaving program by Andrew Glassner ; associated blogpost 

11/26/17 a simple, user-friendly free motif design paint program for Mac, last updated April 2019: Paint Brush

Atkinson dither github (free)

I have linked before (March 14, 2013) to this github as a way to achieve atkinson dithered images for possible use in knitting. I received a post with questions on how to achieve this successfully. I work on a Mac, latest OS. The resulting dithered files were not read when downloaded by any app other than Preview, and resizing within program was poor quality. Here is my work-around: it is always best to resize any of the images to be processed in color or grey scale, before indexing modes or dithering. Once that is achieved, import image into github without changing output size in the program itself, and download. Your own image size will be retained. Now time for another freebie intervention: XnConvert will accept the file, convert it to BMP or other readable formats if preferred, resulting in a knittable image.

the sized image

hyperdithered.png

via github_XnConvert_.bmp

…

Converted images,”representational knitting”

One bit camera “snaps pictures in digital retro style. I began this tale with a partial shot of my face. The app apparently is no longer available via US App Store (11/15/2017)

resized, greyscale, knittable size bmp

The old bag of tricks did not produce an image I was happy with, I finally used Ggraphicconverter Picture_Mode_ Bitmap for my downloadable file

Migrated from Mac to a PC laptop, opened in WinCrea, the image repeat was downloaded to Passap, program tech 179. The bottom  of the swatch is knit single bed LX (slip stitch), the top is double bed, back bed set N/N, same tension throughout, the middle stripes are operator error in forgetting to make the lock change to LX on the front bed; the gauge is significantly and obviously different

Moving on to a birds’eye backing, the bottom starts the pattern with dark color, top with light (another operator error and a reminder to keep notes even for what may seem obvious); the black is slightly thinner than blue resulting in a change in gauge once again

The bouncing gauges certainly indicate some of the problems in maintaining aspect ratios in representational knits. The best solution may be to do a large swatch in the planned technique that is at least 100 sts X 100 rs in chosen yarn and then adjusting image aspect ratio before knitting the final piece, which in turn may be better done before conversion to final BMP and require repeating the process from its beginning.

For separations such as technique 179, and those by default in Japanese machines for 2 color DB, images must have an even number of rows in length. My original image crop was 73W by 85L pixels, so I had to shorten it by one row, which was actually achievable within WinCrea. The single bed FI swatch measured 7 inches in width, the double bed ones 12 inches at their widest point.

Last but not least, here is my friend Rocco processed via Hyperdither, Mac to PC, to WinCrea, to Passap and knit 150X150 pixels/ stitches

May 24, 2019 a greyscale mode scaled image processed in ditherlicious online produced a sharper, far more defined image than my previous effort 142X146 pixels

for more Rocco “portraits” see post

GIMP and dithering color reductions for B/W “portraits”

The many faces of Rocco: in my 2013 tests in Gimp, the image is 150 pixels wide by 154 pixels high  The image is used with the kind permission of Rocco’s owner. I have used this image before, when I posted previously on some ways to reduce colored images to B/W for possible knitting using a Mac computer, please see post on 013/03/14/ color-reduction- conversions-mac-os/. Gimp offers some alternatives to the familiar dithers and is available, free, for both PC and Mac platforms. Tutorial links on Gimp edge detection available online as of May 2019 are listed at bottom of the post.

Image_Mode_Indexed_ one bit black: immediate result, too dark

Threshold adjustments may not be made in indexed images to alter the above image, so it’s back to greyscale. Reductions to greyscale may be achieved through Image_ Mode_ Greyscale or choosing Colors_Desaturate_OK options. Desaturation offers additional choices

Image_Mode_GreyscaleColors_Desaturate_OKRocco desaturated, in “knittable portrait size”using edge detection and its algorithmsDifference of Gaussians

what happens if in addition color_ invert is used with Robertsadjusting B/W with Thresholdafter a bit of “tweaking” Image_Mode_Indexed, rendering it “knittable in 2 colors” getting silly with filling the ground with pattern behind the floating head

2021: the latest, December 2020 updated version of Gimp for Mac OS
Gimp dithering controls easily accessible with mode changes to indexed I found I got the best results adjusting the contrast in the original greyscale image prior to changing its mode to indexed and dithering (Floyd_Steinberg, normal)  Dithering options in Gimp 2.10 may be found at the bottom of the colors menu or when converting to indexed colors, here to black and white, the image unaltered, using positioned dithering, the last option  Hyperdither: options offered  default Jarvis
default Stucki
online, options https://ditherit.com it is possible to choose from multiple palettes Sierra dither

5/4/2019 Other than GIMP: after straightforward load, convert, save, with no other adjustments, images shown in approximate 150 pixels/sts in width, no significant change results with conversion to color B/W indexed
http://gazs.github.io/canvas-atkinson-dither/
online, default settings https://29a.ch/2016/08/04/ditherlicious-1-bit-image-dithering
Check dithered results, downloaded images may be in RGB Mode. Prior to any knitting, they will need to be converted to B/W indexed.
Looking for ways to reduce the noise in dithered images I tried this conversion in XnSketch, using the photocopy effect,  beginning with the colored image of Rocco, the results: imported the result into Gimp and saved it in indexed  2 color BW and in turn, 3 color indexed mode, no color adjustments, finding the result pleasantly simple beginning with the greyscale generated image followed by Mode changes in Gimp, indexed 2 color BW, then indexed 3 color, there appear to be very subtle differences with a bit more detail: Another online resource with an extensive array of dithering options https://app.dithermark.com. Here are 2 conversions using the app, the images are 2 color B/W. The presence of a third color is an illusion created by the difference in the distribution of BW color pixels, they loaded fine as viewed for knitting in Ayab, and in img2track, once I remembered to change its setting to 2 color knitting from the last used one at 4 colors It is possible to reduce images to 4 or 3 colors using the program as well: a slider for color count is used to choose the final number of colors in the reduction. Again, these instances have no added manipulation A series of dithers:
To retain the quality and size of the dithered image, download it, rather than using a screen grab. The software used to separate the chosen dither may alter the result somewhat. I am writing my posts using an iMac M1 with OS 12.0.1. At this point Ayab is not operable, img2track does open images, but in this case, with interesting distortions, and it does not download any files at all. Yet another dithering tool, allows one to draw in dithering mode using a variety of patterns and will dither images. In the latter instance, there is no real opportunity to tweak or alter the result shapes drawn using a few of the large variety of offered patterns: 

 

Color reduction/conversions, Mac Os

A recent forum post brought up the question that rises periodically on how to reduce colors in photographs, scans, etc. so as to be able to in turn use the image in a low-resolution medium such as knit. There are very many ways to achieve this. The post had specifically asked for low cost or free alternatives using Mac software, so I began playing, and compiled the following document detailing some of my processes, addressing large scale, non-repetitive images in Color reductions for knitting. The document samples were simple, straightforward conversions, with no further “tweaking”.

Mac Os: iPhoto, Preview, further software downloads:

Free:  img2trak, HyperDither, XnConvert

99 cents One bit Camera
an option for Mac users, Bitcam

Free to try, $39.95 to buy GraphicConverter, the developer site
diffusion, halftone, pattern, custom A tutorial for owners of Photoshop   diffusion, halftone, pattern, custom With thanks to my test subjects: RoccoOne bit camera and my sofa fabric

An online service that will do the conversion for you: Knitpro, and a free service GitHub May 2019: ditherlicious

A later post on the topic, showing the many faces of Rocco