Resize PNG ignores specified depth

[gohanman]

I have a PNG with 1-bit color. I'm trying to resize it. Identify shows this for the original:

Code: Select all

  Format: PNG (Portable Network Graphics)
  Class: PseudoClass
  Geometry: 180x192
  Type: Bilevel
  Endianess: Undefined
  Colorspace: Gray
  Channel depth:
    Gray: 1-bits
  Channel statistics:
    Gray:
      Min: 0 (0)
      Max: 1 (1)
      Mean: 0.596644 (0.596644)
      Standard deviation: 0.490571 (0.490571)
  Colors: 2

If I resize it like this:

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convert -resize x115 -depth 1 original.png smaller.png

The resulting file looks like this:

Code: Select all

  Format: PNG (Portable Network Graphics)
  Class: DirectClass
  Geometry: 108x115
  Type: Grayscale
  Endianess: Undefined
  Colorspace: Gray
  Channel depth:
    Gray: 8-bits
  Channel statistics:
    Gray:
      Min: 0 (0)
      Max: 255 (1)
      Mean: 152.01 (0.596119)
      Standard deviation: 116.442 (0.456636)
  Colors: 246

How do I resize the image while retaining 1-bit depth?

[snibgo]

The correct order for commands is in the logical chronological order. In this case: read the image, resize it, set the depth, write it. Try that.

[glennrp]

If you "resize" an image there are likely to be more colors in the output than in the input due to interpolation. Use "-sample" to avoid adding colors and
then you shouldn't need to specify the depth.