View Full Version : Save Qt tiff files in 1 bit not 32 bit

19th June 2009, 22:07
Anyone know how to save a black and white tiff file in "2 colors" not "millions of colors"?

Qt saves them as 32 bit but I only need 1 bit (QImage::Format_Mono)

Or does Qt have another format that can save black and with images in the smallest size possible?

Thank you, Jeff.

20th June 2009, 02:30
Mono is one bit (2 colours), not two (4 colours)... Storing one bit images as tiff and expecting them to be small is a dead man's wish. Use PNG instead, it offers a decent compression and is loseless format just like tiff.

20th June 2009, 02:49
I wish I could use png but our "old" imaging system only works with tiff files.

The tiff files on our imaging system are about 1/2 to 1/3 the size of the qt tiff lzw compressed files.

I might pull the tiff plugin source and create a local 1 bit write function.

Thank you for the idea.


20th June 2009, 10:25
If tiff supports a 1bit image format (I don't know if it does, tiff is mostly used for photos, not mono bitmaps) then saving it as such should have worked.

20th June 2009, 10:52
Tiff is a sort of meta-fileformat, it can support any colorspace, any compression and custumn meta tags. So you could have a scanner that likes outputting images with 1 bit for black-white and 13bits for shades of purple ... all compressed with let's say the rar-algorithm.

So working with tiff really is no fun. Qt4 works with 32bit ARGB internally and as far as I know cannot be told to work with other stuff. blowing up 1bit image data to 32bit looks like a waste of space. So if you need fast processing of lot's of images, you might be faster with your own implementation.