Need help with green and blue polka dots

Discussion in 'Photoshop' started by liaM, Oct 4, 2007.

  1. liaM

    liaM Guest

    I'm stumped by the following problem : the photo consists of a yellow
    background to hundreds of green and blue polka dots ; how can I make all
    of the green polka dots disappear into the yellow background (while
    keeping the blue polka dots intact) ?

    How to do this in one go, and not having to erase the dots one by one ?

    PS. I use Photoshop 5
    liaM, Oct 4, 2007
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  2. liaM

    Mike Russell Guest

    Good puzzle. Use a mask combined with a curved version of your original
    image as follows:

    Duplicate the image, and convert the duplicate to Lab mode. You'll be using
    the a channel of this image as a mask.

    Duplicate the original image to a new layer, and copy the a channel of the
    Lab image to the layer mask of the duplicate layer. The quickest way to do
    this is to use Image>Calculations to copy the b channel as a selection to
    the original document, then create a layer mask to show the selection. The
    polka dots, which will be light colored in the a channel - use Levels to
    bump the contrast of the layer mask, and add red to the duplicated layer
    until it matches the yellow background. It will take some fiddling to get a
    good match, and to eliminate fringes from what is left of the green polka
    dots. You may find Image>Adjust>Hue/Sat to be helpful in getting a good
    match to the yellow.

    I haven't actually tried the above procedure, so it may contain errors. The
    principal is to use the a channel as a mask for the green parts of the
    image - blue and yellow are absent from this layer so there should be good
    selection for the green dots, with very little crossover between luminance,
    or the blue and yellow areas.

    Perhaps you can post the image and some of us can give it a try.
    Mike Russell, Oct 4, 2007
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  3. liaM

    liaM Guest

    Hi.. I'm totally mystified by your text. It doesn't help that I'm
    using a french version of photoshop 5. I'll have to figure out what is
    meant by "channels".

    But it still seems to me there must be a simpler way to proceed that
    doesn't require fiddling (I'm not much good at playing in tune!).

    I'd wish to use the eyedropper to memorize the colors of the green dots
    and the yellow background. Then I'd want a command such as "search and
    replace" every instance of the stored color green with the stored color
    yellow. Doesn't that exist in photoshop ?

    Thanks again !
    liaM, Oct 4, 2007
  4. liaM

    KatWoman Guest

    try this
    SELECT >color range
    move slider until only green dots are selected
    or just magic wand all the green dots

    make a new layer
    select expand a couple of pixels if you want to feather it a bit too
    then eye dropper the yellow color
    edit >>fill the selection>>> with the yellow
    KatWoman, Oct 4, 2007
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