I have .png image which represents relief shadows. I need to save it in Photoshop 1-bit .png. Can someone help me, please?


2 Answers 2


Do you mean 1-bit as in black & white or single color with an alpha channel?

Just about any imaging app can do both - an image converted to black & white in M$ Paint, is essentially a 1-bit image. In PhotoShop, you can create a regular 8-bit image, File->Save for web, set it to PNG-8, transparency ticked, then set the number of "colors" to 2.

It would be the same as the black & white image, but a color (yes, black counts) & alpha channel (transparency).


Believe boofighter wants to convert an existing .png image into a monochrome .png file. Monochrome .png files have pixels represented by only a single bit, with the display of each pixel having only two possible states, either black or white.

The query "1-bit .png" in is taken to mean a .png file with a bit depth of 1. On windows machines, one can see the bit depth of a .png file.

from the windows Start button... right mouse click on Start...
windows explorer...
navigate to the location of a .png file...
right mouse click on a .png file...
properties row of the pop-up...
details tab of the dialog...
enter image description here

The "bit depth of a .png", characterizes the number of bits allocated to each pixel. A higher bit depth means each of the pixels in that .png can represent more different values. Many color .png files have a bit depth of 24 with 8 bits for each of Red,Green,and Blue. These files have potentially 256 values for Red (with those values being 0 through 255 inclusive), a similar potential for 256 different values for Green, and a similar potential for 256 values for Blue. The total number of different colors which can be represented in a 24 bit depth .png is thus 256 red x 256 green x 256 blue = 16,777,216 different colors. Many .png files referred to as "black & white" are actually grayscale images with a bit depth of 8. These greyscale files have 256 potential values for grey values with the extreem of 0 for the darkest of greys (known as black) and 255 for the lightest of greys (known as white).

The MS_Paint reference in the answer by tahwos is not actually correct. Paint has an option labeled "Black & White" which will indeed present an image with pixels with only two values, either black or white. The file continues to have the same bit depth as the input file, not the requested 1-bit .png

ImageMagick (downloadable from https://imagemagick.org/script/download.php ) can convert color and greyscale .png files into monochrome .png files.

ImageMagick has a GUI but (unfortunately) I have not been unable to perform the desired conversion from within the GUI.

One CAN invoke the ImageMagic conversion to monochrome from the Command Line Interface (CLI). The CLI command to create a monochrome .png file named bitDepth1Output.png from a color .png input file named higherBitDepthInput.png is:

magick higherBitDepthInput.png -monochrome bitDepth1Output.png

ImageMagik has a large number of conversions available. They are listed at https://imagemagick.org/script/convert.php

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