| | <<<Back 1 day (to 2016/06/08) | 20160609 |
| psmlbhor | Hello. I have some PWG raster files which I am converting to Postscript files using colorimage command and writing the data in hex format. But the output files produces are 500 MB in size. Is there any way I can reduce the size of PS files ? | 04:55.02 |
| | can anyone help me please? | 06:55.05 |
| kens | Its not yet 8 am here in the UK and its the middle of hte night in the US. | 06:55.38 |
| psmlbhor | Oh! Sorry I didn't thought about that. I will wait | 06:56.39 |
| | kens, can you help me with that? | 06:57.07 |
| kens | I've just read your question and I don't see what you are expecting. A bitmap file has a lot of pixels in it, so its always going to be large. | 06:57.44 |
| | You can, of course, apply compression and then write the PostScript to apply a decompression filter. | 06:58.00 |
| | Using binary instead of hex string would also reduce the size considerably | 06:58.22 |
| psmlbhor | but won't binary occupy 4 times the space for each hex character? | 07:00.38 |
| kens | Well no | 07:02.17 |
| | 0xFF is one binary byte, in hex its 2 bytes | 07:02.52 |
| psmlbhor | ok. I will try this out now. Thanks | 07:05.11 |
| halabund | Are there any free PostScript viewers based on Ghostscript for OS X? | 08:14.04 |
| kens | Yes, Ghostscript | 08:14.13 |
| halabund | Iâm using gv, which is X based. Anything better? | 08:14.15 |
| | h | 08:14.20 |
| kens | I guess you need to define 'better' | 08:14.36 |
| | Ghostscript itself will render to an X terminal window, gv is kind of old, and I'm not really familiar with it | 08:15.13 |
| halabund | kens: I would like the ability to zoom, pan and hopefully not be X based. Otherwise Iâll just stick to gv. | 08:15.29 |
| kens | Well, one of our developers wrote a (ground up) new version of GSView, but I don't remember if it runs on a Mac. | 08:16.23 |
| | Seems it exists: | 08:17.32 |
| | http://www.gsview.com/downloads.html | 08:17.32 |
| | There's an OS/X link there. I've no idea about it's capabilities though | 08:17.55 |
| | One thing you might need to bear in mind is that it uses GS to convert PostScript to PDF, and tehn views the PDF | 08:18.18 |
| halabund | Thank you! There probably isnât anything better for Mac then, except paid solutions. Preview usually opens EPS files so most people donât need it. And otherwise theyâd convert to PDF with another tool than Preview and view the PDF anyway. | 08:18.29 |
| | Ah, sorry | 08:18.49 |
| | I thought I was looking at the same link | 08:18.54 |
| | this is something different | 08:18.57 |
| kens | Yeah, up to version 6 GSView is a Linux/WIndows thing (mainly Windows) by Russell Lang of Ghostgum | 08:19.32 |
| | THe new version is ours, but it works differntly | 08:19.47 |
| ferter | hi! may i ask you, if saving password-protected pdf is somewhat different from saving ordinary files in mupdf? | 08:20.52 |
| kens | ferter you want to take a PDF and add a password to it, or take an existing secured PDF and save changes ? I can't answer either way I'm afraid, but it'll save time when someone comes along who can answer | 08:21.52 |
| ferter | i have an existing secured PDF. when i add annotations and to save them, AP won't work properly when i reopen a saved file. this bug appears ONLY with secured files, i've checked that carefully! | 08:24.06 |
| halabund | kens: Thanks! GSview 6 does what I need. | 08:24.09 |
| kens | Ah good, hope it helps you out | 08:24.19 |
| halabund | (Illustrator doesnât though, it doesnât put the a bounding box that corresponds to the artboard in the EPS.) | 08:24.33 |
| kens | I guess the problem is which Box to use when creating an EPS, MediaBox, BleedBox, TrimBox, CropBox, ArtBox..... | 08:25.19 |
| | ferter I recently discovered that saving a repaired file didn't actually repair the file, this may be a related problem. | 08:25.45 |
| | Hopefully Robin_Watts will be able to say more when he comes online | 08:26.15 |
| ferter | kens, ok thank you. what is a repaired file, though?) | 08:26.40 |
| kens | ah, if a PDF file is invalid in some way (eg the xref table is incorrect) MuPDF will repair the fault. It then offers to save the repaired file. However that doesn't seem to work now (it did). I'm speculating that there may be a similar problem affecting secured files, because a modified file has new objects, and the encryption key uses the object numbers. So it may be that rewriting PDF files has some kind of problem similar to the repair b | 08:29.11 |
| kens | hunts more coffee | 08:30.01 |
| ferter | all right, gotcha | 08:34.33 |
| kens | Of course, it may simply be that the PDF rewriting code doesn't support encrypted files, for the reason that the new object(s) number need to be encrypted. I don't know enough about MuPDF, but someone will be able to answer shortly I expect | 08:35.54 |
| ferter | hope so) | 08:41.32 |
| Robin_Watts | ferter: MuPDF can't write encrypted files. | 09:10.47 |
| | It *should* allow you to save files without encryption once you've added stuff, but it's possible that yesterdays bug might be biting us there too. | 09:12.14 |
| ferter | Robin_Watts thank you for the feedback | 09:32.33 |
| Robin_Watts | ferter: If you open a bug, and attach a file before and after adding AP's, I'll have a look. | 09:33.01 |
| | It may be I need to tweak the pdf_can_be_saved_incrementally function a bit more. | 09:33.18 |
| ferter | Robin_Watts i will do it, if it helps. but i don't now how | 09:34.24 |
| Robin_Watts | Go to bugs.ghostscript.com. It's all obvious. | 09:34.39 |
| ferter | Robin_Watts done | 09:48.12 |
| Robin_Watts | thanks. Give ma a couple of days.. | 09:48.55 |
| ferter | you are welcome, sir | 10:04.00 |
| halabund | If I use -r600 with eps2write, while converting a PDF, will it resample higher resolution bitmaps to 600 dpi? I need everything to be at most 600 dpi, no higher resolution. | 10:55.45 |
| kens | Not by default | 10:56.02 |
| | You can use the relevant controls to set the image resolution threshold and downsample type though | 10:56.25 |
| | See VectorDevices.htm in /ghostpdl/doc in the current release | 10:57.07 |
| | BTW setting -r600 only affects the resolution of objects which Ghostscript renders. SO if the input was a PDF with transparency, the output would be an image at the specified resolution. Other images, and the accuracy of vector objects, are not affected by '-r' | 10:58.50 |
| halabund | BTW is it true that using higher resolution can cause a bad quality output? | 10:59.25 |
| | Because thatâs what the journal told me. That it mustnât be higher than 600 dpi or it will look bad. I donât understand how that is possible. | 10:59.47 |
| kens | It should not, no. But its not clear to me what you mean by 'bad quality' | 10:59.52 |
| Robin_Watts | halabund: If you have images at 800 dpi, and then they actually get rendered at 600dpi, then depending on the techniques they use, you might get dropout. | 11:00.36 |
| kens | If you are printing at 600 dpi, and the input is higher resolution than that, then the input obviously will be reduced, and the method used is device-dependent. SO it depends what is being used to do the job. | 11:00.41 |
| Robin_Watts | This will be especially noticeable with halftoned images (images that are halftoned in your source document) | 11:01.04 |
| halabund | To quote, they said âImages in Figures 1-4 and 6-11 are high resolution and may not look good when published.â âPlease carefully review the Figure Guidelines and ensure that any images placed within your Figures do not exceed 600 dpiâ | 11:01.34 |
| kens | Well, its like Robin said. COnsider a 1 pixel horizontal line at 1200 dpi. WHen we print that at 600 dpi, using a simple solution like subsampling, its possible the entire horizontal line might be dropped. | 11:02.31 |
| halabund | OK, second question: is it possible to use Ghostscript to get rid of all transparency in a PDF (and then output EPS)? It will be completely acceptable to just set the opacity of any transparent objects to 1 (fully opaque). | 11:03.19 |
| | I donât expect it will be possible ... | 11:03.26 |
| kens | Using a better 'but more computationally intensive) downsampling algorithm would perhaps change the 1 pixel black line into a 1 pixel gray line instead | 11:03.33 |
| halabund | ⦠but I wanted to ask as it would save me some time. | 11:03.35 |
| kens | If you have a transparent PDF as input, and convert to PostScript, there will be no transparency. However, the result will be that the pages ocontaining transparency will be rendered to bitmap images. THis may well not be aqcceptable toyou. | 11:04.22 |
| | You can also (I think) set -dNoTransparency, which will drop all transparency (effectiverly setting it to fully opaque), which will (again, I think) produce an EPS without any transparency, but not rendered to a bitmap. | 11:05.19 |
| | You'd have to try that and check it though, I'm not certain | 11:05.31 |
| | Apparently that should be -dNOTRANSPARENCY | 11:06.26 |
| halabund | Thanks! It sounds like I need -dNoTransparency. Iâll try it. The goal is to avoid rasterization. My plotting software tends to put in unnecessarily transparent lines. | 11:06.34 |
| kens | Its not unusual, Cairo, for example, often adds irrelevant transparency operations | 11:07.08 |
| kens | lunches | 11:12.30 |
| halabund | OK, so Iâm trying to get gs to downsample high res images embedded in a PDF, and output an EPS | 11:34.10 |
| | I use this: | 11:34.12 |
| | gs -sDEVICE=eps2write -r600 -sOutputFile=Fig11.eps -dBATCH -dNOPAUSE -dDownsampleColorImages=true -dColorImageResolution=600 Fig11.pdf | 11:34.31 |
| | It doesnât seem to downsample though | 11:34.38 |
| | What am I missing? | 11:34.40 |
| | I also added -dColorImageDownsampleThreshold=1.0, but no effect | 11:37.33 |
| | is this because I am using eps2write instead of pdfwrite? Are these specific to pdfwrite? | 11:37.49 |
| Robin_Watts | halabund: You will need to wait for kens to get back from lunch. | 11:39.09 |
| halabund | In case I accidentally disconnect, I am going to check the channel logs! | 11:41.38 |
| kens | is back, let me catch up | 11:44.47 |
| | The parameters are not specific to pdfwrite, we do use them for ps2write and eps2write as well,though I appreciate this may be confusing. | 11:45.41 |
| | Its one of the reasons I rewroter the documentation. | 11:45.55 |
| | Well, if you set DownsampleColorImages, ColorImageDownsampleThreshold and ColorImageResolution, it *ought* to work as far as I can see. | 11:47.35 |
| | If you have an example file you can share I can look further, otherwise I'll try and find one here. | 11:48.00 |
| halabund | Iâll share it | 11:49.07 |
| kens | Saves me rummaging through PDF files, thanks | 11:50.21 |
| halabund | Iâm using 9.19 from MacPorts btw. | 11:55.01 |
| kens | halabund : it looks like there might be a big here. When we try to decide whether to downsample or not the pointer tot he CTM is always NULL. Without knowing the CTM we can't work out the effective resolution of the image, so we don't know that we should downsample it. | 12:03.45 |
| halabund | what is the CTM? | 12:04.16 |
| kens | Current Transformation Matrix | 12:04.24 |
| | Its the method for converting between user space (infinitely scalable) and device space (real pixels) | 12:04.50 |
| | We need to know how what the DPI of the image is before we can decide whether to downscale or not. We do that by finding out how much of the page it covers and then dividing by the number of pixels in each direction in the image data. | 12:05.41 |
| | But we need the CTM to figure out how big the image is, and we don't have it. THat seems to be a bug, and I'm sure this worked previously :-( | 12:06.06 |
| halabund | Is there anything I can do while producing the file to make it more likely that I wonât hit this problem? If not, itâs no big deal, Iâll just take a ruler, measure and approximate how many pixels I should use. | 12:06.34 |
| kens | There's nothing you can do, this is internal in the devioce code | 12:06.49 |
| halabund | OK | 12:06.53 |
| | Thanks for looking at it :-) | 12:07.01 |
| kens | I'll carry on looking at it, I need to fix this if its a bug | 12:07.13 |
| | Its *supposed* to work :-( | 12:07.23 |
| | ah, it looks like the problem is that because its PostScript output, we do images inline, so we set 'lossless' filters, and that drops the graphics state. I expect I cna fix that. Looks like nobody ever tested this before. | 12:11.33 |
| | halabund I fixed the problem, but it seems that your images, as drawn, are not > 600 dpi. I'm getting a resolution of 391 dpi for the first, and 300 for teh second. | 12:21.42 |
| halabund | @kens Thank you! I wasnât sure they were 600 dpi, but I tried decreasing the setting all the way to 50 and the file size didnât change. Thatâs why I was convinced that something is wrong. | 12:22.59 |
| kens | Oh yes, there's definitely a bug as well, I've got a fix for that as well but I need to test it. | 12:23.31 |
| | With my fix changing from 600 dpi to 200 dpi drops the file size from 3.3MB to 1.27 MB so it seems like its working. | 12:25.39 |
| | Seems like ColorImageDownsample also isn't being set, need to fix that too | 12:27.09 |
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