That problem doesn't arise with the GUI solutions you posted, I presume. Even when the background colour was 255 255 255, the paletted value wasn't pure white. It seemed to be necessary to determine the actual paletted colour in a test conversion so that that value could be set, the actual value depending on the bit depth valued entered. That seemed to work well for the letters I tested initially which were black and white scans (so no need to use 256 colours really) but failed when I tested a colour scan: the problem seemed to be that when the image was converted to paletted colour, nominally white canvas wasn't converted to pure white even when I reduced the colour depth right down to 8 colours. At a quick look the following options support transparency:Ĭode: Select all nconvert -32bits -colors 256 -transpcolor 255 255 255 *.PNG That could be useful if the need arose regularly, although that isn't my present use case. Having converted a letter and now done a further test I'm not sure if the result is actually better.Īfter posting yesterday, as an afterthought I checked the NConvert help file and found that it might be possible to create a batch file that would convert scans to transparent in a single operation. I'd done some tests using layers in Paint.NET which I've worked with a little recently, but then wondered if starting with a transparent foreground image of the letter might produce a better result, or have other advantages. I thought it might look better if the passages to be marked were highlighted by a single coloured block. My considered use case arises directly from my freely-admitted perfectionist personality trait: I need to prepare a file containing copies of a series of letters in which carefully selected text is highlighted I could of course easily use the highlighting tool in Adobe Acrobat, but I noticed that it can leave gaps between the lines marked. Thank you for your customary detailed response: not only possible, but a choice of methods.
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