Need help to improve special scanned images

[fmw42]

!)Adding "-transparent color" increases the image bit depth form 1 to 32. How can it be fixed? The final png image only contains a black color and transparent, that requires one bit depth(2 different colors). If impossible, then how could the bit depth be decreased to 4 instead of 1?
2)How can I change the image distinct black color darker? It has now a gray level and I want it be pure black?

1) IM support of PNG formats is limited, if not PNG32. See http://www.imagemagick.org/Usage/formats/#png_formats

You can try saving as PNG8:yourimage.png

or try using GIF.

Others may be able to help further.

2) I am not sure what you want or what you image looks like.

You can try -black-threshold XX% or -black-threshold XX where the latter is graylevel measure per your Quantum Depth compile of IM (Q8 0-255, Q16 0-65535)

See http://www.imagemagick.org/script/comma ... -threshold

Otherwise, post a link to your image

[Drarakel]

Saving transparent images as palette PNG (overall bitdepth lower than 32) is possible with some older ImageMagick versions. But not with a current version. (Trying that usually results in losing the alpha channel.) You should indeed check out the 'non-ImageMagick PNG' tools like pngout or OptiPNG. It's recommended anyway to process your final PNG output files with one of these tools if you want them to be smaller.

[amirian]

Saving transparent images as palette PNG (overall bitdepth lower than 32) is possible with some older ImageMagick versions. But not with a current version. (Trying that usually results in losing the alpha channel.) You should indeed check out the 'non-ImageMagick PNG' tools like pngout or OptiPNG. It's recommended anyway to process your final PNG output files with one of these tools if you want them to be smaller.

Thanks, I succeeded using pngquant. But this is too bad that IM ability reduces while its version goes up!