Thanks to the respondent below. On my present printer I can't cahnge to CMY only, it has very restrictive drivers. Also I use several printers from tiome to time and would like to solve this for all.

Yes, dark blue has a lot of black in it but in my experience you can always find some colour that the printer will print pretty "dark", whetehr it be a dark grey or a dark other colour, that in a pinch will do for readable text, or a scannable barcode, or a diagram. Over the years I get this issue a fair bit, can't print absolute black but can print something close.

So, can anyone just step me thru the Gimp steps for doing this ?

Many thanks (or indeed atdhvaannkcse) Greg E.

On Wednesday 02 September 2009, Greg Edwards wrote:

Hi,
The scenario - have an inkjet printer which regularly runs out of black ink, but still has plenty of colour ink. I would like to change black to dark blue or whatever, so I can print eg. a concert ticket with a black barcode, which will still scan fine at the venue entrance.

On SGI in Days of Olde, this would be " repcol ticket.rgb 0 0 0 0 0 20 10 " or similar, ie. replace all pixels within 10 units (out of 255) of black with dark blue. Good old Paul Haeberli and his gfx tools.

Appreciate assistance in doing this in Gimp - 2.6.7 on Mac with Snow Leopard (10.6). Or indeed a command line tool of any kind, I need this little trick quite a bit.

ATdhvaannkcse !

Greg E

Wouldn't it be the easiest way to set the printer to use CMY only instead of CMYK? Many printer drivers can do this.

A dark blue would still consist of a lot of black since GIMP only knows about RGB and only when printing this is converted to a more printer-native representation.