access image properties in Lua
What’s the current approved way to get image properties within a Lua function? very old: local pic = figures.getinfo(figures.current().status.fullname) used to work in 2019: local pic = img.scan{filename = figures.current().status.fullname} if I understand this right, "img" isn’t valid anymore: """ token call, execute: grph-imagelib.lua:37: attempt to index a nil value (global 'img') """ I’d like to know the pixel size and if possible also the scaled target size of an image; either the "current" one or by name. Hraban
On 7/11/2023 2:22 PM, Henning Hraban Ramm wrote:
What’s the current approved way to get image properties within a Lua function?
very old: local pic = figures.getinfo(figures.current().status.fullname)
used to work in 2019: local pic = img.scan{filename = figures.current().status.fullname}
if I understand this right, "img" isn’t valid anymore: """ token call, execute: grph-imagelib.lua:37: attempt to index a nil value (global 'img') """
I’d like to know the pixel size and if possible also the scaled target size of an image; either the "current" one or by name. \ctxlua{inspect(figures.getinfo("t:/sources/mill.png").used)}
\ctxlua{inspect(figures.getinfo("t:/sources/mill.png").status)} etc .. no more faking the img lib Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl -----------------------------------------------------------------
On 13/07/23 13/07/23, 09:19, Hans Hagen wrote:
On 7/11/2023 2:22 PM, Henning Hraban Ramm wrote:
What’s the current approved way to get image properties within a Lua function?
very old: local pic = figures.getinfo(figures.current().status.fullname)
used to work in 2019: local pic = img.scan{filename = figures.current().status.fullname}
if I understand this right, "img" isn’t valid anymore: """ token call, execute: grph-imagelib.lua:37: attempt to index a nil value (global 'img') """
I’d like to know the pixel size and if possible also the scaled target size of an image; either the "current" one or by name. \ctxlua{inspect(figures.getinfo("t:/sources/mill.png").used)}
\ctxlua{inspect(figures.getinfo("t:/sources/mill.png").status)}
etc .. no more faking the img lib
Hans
Hraban, Hans, and mailing list. This is interesting. I would find it useful to be able to report these properties though a tracker - should be fairly easy if not already available. One works with images having a certain resolution, whatever that may be. We also might have a target resolution, say 300 dpi or perhaps better for printing. As the images are typically resized when used, the resulting resolutions might be anything. Optimizing the resolutions of the source images can result in optimal PDF sizes, i.e. not too high nor too low resolution. I can even imagine an automated workflow where high-resolution, say 2400 dpi or even greater bitmap images, are supplied and the included bitmap could be "resampled" resulting in the inclusion of a targeted resolution. However, the reporting of the included, likely resized image resolutions then used to adjust or resample the source files externally and manually case-by-case would be sufficient. Any suggestions on how to hook-in such reporting? Bonus question: how also to handle the case of \startMPcode draw figure "MyFigure" xsized TextWidth ; ... \stopMPcode -- Alan
Am 17.07.23 um 15:44 schrieb Alan Braslau via ntg-context:
On 13/07/23 13/07/23, 09:19, Hans Hagen wrote:
On 7/11/2023 2:22 PM, Henning Hraban Ramm wrote:
What’s the current approved way to get image properties within a Lua function?
I’d like to know the pixel size and if possible also the scaled target size of an image; either the "current" one or by name.
\ctxlua{inspect(figures.getinfo("t:/sources/mill.png").used)}
\ctxlua{inspect(figures.getinfo("t:/sources/mill.png").status)}
etc .. no more faking the img lib
Thank you!
We also might have a target resolution, say 300 dpi or perhaps better for printing.
What raster widths are you printing with? More than 300 dpi would be only needed for very high resolution art prints with very fine details, possibly in FM raster. Usually, 200 dpi final resolution is enough – 300 dpi are suggested to allow for some scaling. For fine line art (black or spot color only, no rastering), 1200 dpi is suggested.
I can even imagine an automated workflow where high-resolution, say 2400 dpi or even greater bitmap images, are supplied and the included bitmap could be "resampled" resulting in the inclusion of a targeted resolution. However, the reporting of the included, likely resized image resolutions then used to adjust or resample the source files externally and manually case-by-case would be sufficient.
Well, I was working for years with adapted versions of Peter Münster’s graph-downsample.lua. You can hook in custom functions like this: """ \startluacode local function downsampler(oldname, newname, resolution) if not resolution or resolution == "" then resolution = 72 end local cmd = string.format( [[gm convert -resample %ix%i %s %s]], resolution, resolution, oldname, newname) --print(cmd) os.execute(cmd) end -- Beware: the calculation is still wrong, -- I need to try figures.getinfo -- Set the PDF and default JPEG converters to the above function. --figures.converters.jpg.downsampler = downsampler figures.converters.jpg.pdf = downsampler figures.converters.jpg.default = downsampler \stopluacode \setupexternalfigure[ conversion=downsampler, resolution=200, ] """
Any suggestions on how to hook-in such reporting?
local report = logs.reporter("alan.imaging") report("Now calculating...")
Bonus question: how also to handle the case of \startMPcode draw figure "MyFigure" xsized TextWidth ; ... \stopMPcode
Is MyFigure a pixel image? You could use \externalfigure within MP code. Hraban
On 17/07/23 17/07/23, 18:20, Henning Hraban Ramm wrote:
Bonus question: how also to handle the case of \startMPcode draw figure "MyFigure" xsized TextWidth ; ... \stopMPcode
Is MyFigure a pixel image? You could use \externalfigure within MP code.
The MP operator figure calls \externalfigure. However, the resolution downsampler hooked into externalfigure as you suggest would not give the desired resolutions once resized in MP. A solution might be to use draw rawtextext("\externalfigure[MyFigure][width=\textwidth") ; which is OK for this simplified example but would not work when more sophisticated MetaPost transformations might be needed. Along the lines of the conversion downsampler, a resolution reporter and manual resampling could be more efficient than reconverting the bitmap image at every run, of which there can be many. -- Alan
participants (3)
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Alan Braslau -
Hans Hagen -
Henning Hraban Ramm