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Thread: Grayscale image is designated as color by the Paint tool

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    IV Beginner ineuw's Avatar
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    Default Grayscale image is designated as color by the Paint tool

    I work with grayscale images converted by the batch processing tool. Some of the images are interpreted as color when I open the Paint tool color dialog. The batch processing is always set to 256 colors and always convert to "grayscale". How can I correct this to keep the image grayscale at all times?
    Irfanview 4.54, Win 10 Pro 64bit 16gb RAM, Intel UHD graphics

  2. #2

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    Setting the 256 colors is unnecessary, conversion to grayscale produces 256 "colors" anyway.

    What image format do you use? Are the pictures interpreted as grayscale, when you open them in IrfanView before using the Paint tool?
    IrfanView 4.56 64bit, Windows 10 20H2

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    I am using the batch conversion tool from .jp2 to .jpg. Also, Ctrl-g does not always work, but selecting grayscale from the menu works.
    Irfanview 4.54, Win 10 Pro 64bit 16gb RAM, Intel UHD graphics

  4. #4

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    Try using some different format for intermediate files, for example PNG. JPG uses a lossy compression, so it's not recommended using JPG for storing pictures intended for further editing.
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    IV Beginner ineuw's Avatar
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    Thanks. Will return and post the results of .png conversion as the editing format, and then the final save in .jpg. In the end it's uploaded to Wikimedia Commons, and have done nearly 20,000 images over the years.
    Irfanview 4.54, Win 10 Pro 64bit 16gb RAM, Intel UHD graphics

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    Batch or manual conversion from .jp2 to .png is worse. All images ended up as color, even though grayscale was selected. Conversion from .jp2 to .jpg, only some of the images ended up as "color".
    Irfanview 4.54, Win 10 Pro 64bit 16gb RAM, Intel UHD graphics

  7. #7

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    What's your exact conversion settings? I've tested batch conversion to grayscale PNG and it worked for me.
    IrfanView 4.56 64bit, Windows 10 20H2

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    Quote Originally Posted by JendaLinda View Post
    What's your exact conversion settings? I've tested batch conversion to grayscale PNG and it worked for me.
    Thanks for alerting me to doublecheck the settings. After some changes it now works well. There should be a separate resets to default, one for grayscale and one for colour.

    The cause of the problem seemed to be the 'Colour depth group' in the advanced settings. If enabled, even with 256 colour depth, it generates inconsistent results. I will bring it to the attention of Irfan.
    Irfanview 4.54, Win 10 Pro 64bit 16gb RAM, Intel UHD graphics

  9. #9

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    Conversion to grayscale will actually convert the picture to 256 colors (256 shades of gray), so there's no need to specify the 256 color depth.
    IrfanView 4.56 64bit, Windows 10 20H2

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    Quote Originally Posted by JendaLinda View Post
    Conversion to grayscale will actually convert the picture to 256 colors (256 shades of gray), so there's no need to specify the 256 color depth.
    JendaLinda, again thanks and consider the issue resolved. BTW, do you know of any documentation about the advanced options in Batch processing? I found nothing.
    Irfanview 4.54, Win 10 Pro 64bit 16gb RAM, Intel UHD graphics

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