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Converting an image (JPG, PNG, BMP) into 8BPP grayscale bitmap with no compression

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    Converting an image (JPG, PNG, BMP) into 8BPP grayscale bitmap with no compression

    Hello,

    I am using IrfanView 4.42 64bit version.

    I have some images of different formats. Formats are one of JPG, PNG, or BMP. I need to convert them all into BMP format, 72*72 pixels, 8BPP, compression None.

    When I use batch operations to convert my image collection to above desired format. Final images are all good except Compression is "None, Grayscale" in the final converted images.

    I will be using computer vision training on final images and need to have compression as None.

    My batch operations settings are as follows:
    - Output format: BMP
    - Advanced: RESIZE selected. Width and Height both are set to 72.
    - Advanced: Use resample function (better quality) checked as default. Left as checked.
    - Advanced: CHANGE COLOR DEPTH selected. 256 colors (8BPP) selected. Use floyd-steinberg dithering checked as default. Left as selected.
    - Advanced: Convert to Grayscale selected.
    - Advanced: Apply changes to all pages (TIF/PDF saving) checked as default. Left as selected.

    My original image properties before processing is:
    My converted image properties after processing is:
    My desired final image should have properties like this:

    Any help is appreciated.

    Thanks & regards,
    Ertan

    #2
    File > Save As ..., and choose BMP saves the file as a BMP file. BMP files are not compressed.

    > Advanced: Convert to Grayscale selected.

    You have selected Greyscale so your images are set to greyscale and flagged as being Greyscale. If you don't want the Greyscale to appear, and you do want 8 bit, then select 256 colours. If you do this with an existing greyscale image, the image is no longer reported as being greyscale - it is reported as 8 bit, 256 colours even though all shades are grey.

    Type the desired dpi in the boxes.

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      #3
      One further point that may be important. After you have decreased color depth to 256 colors (8bit) you cannot use Resample when you change the image size. That will always convert it back to a 24bit color depth.

      So either change the image size first and then decrease the color depth, or if you must do it in the reverse order, use Resize when you change image size not Resample.

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