Is it possible to create a tiff file from a postscript-file (created from a pdf-document with readable text and images) into a tiff file without the text and only the images?
There is a way to create a tiff with no images, but I don't know how to use that way for my task. I need it to generate two images from a postscript-file - the first one with the images only and the second one with the text only.
Since the text is drawn over the top of the image, simple clipping won't do the job.
You can hack the text out by redefining the show operators to no-ops. Insert this after the %%Page comment line (where the page code really starts).
/show{pop}def
/ashow{3{pop}repeat}def
/widthshow{4{pop}repeat}def
/awidthshow{6{pop}repeat}def
/kshow{2{pop}repeat}def
/xshow{2{pop}repeat}def
/xyshow{2{pop}repeat}def
/yshow{2{pop}repeat}def
/glyphshow{pop}def
/cshow{2{pop}repeat}def
This will suppress all text-drawing operators. Edit: Now includes level 2 and 3 operators.
If you're trying to selectively suppress different kinds of elements, you may want to redefine only some of these operators. You can add % at the beginning of a line to comment-out a line of the code, keeping the full list intact (for future uses).
Another way to selectively suppress elements from a ps file is to use the powerful clipping mechanism.
144 288 72 72 rectclip % clip to a 1"x1" square 2" from the left, 4" from the bottom
Clip works with an arbitrary path. So you can even string together points in a connect-the-dots fashion to get the effect of a lasso-clip. Probably easiest if you print the image out and trace a grid to easily plot points for the trajectory.
100 100 moveto
200 200 lineto
300 100 lineto
500 500 lineto
200 700 lineto
closepath clip % clip to a non-rectangular convex polygon
Clipping will suppress all drawing operations that fall outside of the clippath while the clipping path is in effect.
Related
I use Gimp, I have a color pallet which contain 556 colors (embroidery related) , but I don't know how to use all those colors in my working image because the index color mode only support maximum 256 colors... what's the solution I have?
All the places in Gimp where the number of colors is limited seem to have an upper limit of 256 colors: indexed mode, color palettes, Posterize filter...
If you want to limit yourself to the 556 colors of your palette, create an image with 556 squares, each painted with one of your 556 colors and save it somewhere. Then when needed open it in Gimp together with your work image, and use the color picker to sample colors from it.
If you want to shoehorn an existing image into your 556 color palette, then you can use the ImageMagick toolbox for this:
Prepare an image with only your 556 colors (as a PNG file, you have to avoid JPEG because the compression will introduce extra colors). This will be your "color map". There is no need for a special format layout, the only important thing is that it contains only your 556 colors (to check in Gimp: Colors > Info > Colorcube analysis, with IM: identify -verbose ColorMap.png and check the Colors line)
Execute the command
convert Source.png -remap ColorMap.png Reduced.png
where:
Source.png is your original image, with likely thousands of colors. It can be any format (JPG, PNG, TIFF...)
ColorMap.png is the map you prepared above
Reduced.png is the color-reduced image. It has to be in a format where pixel colors are preserved exactly (so, PNG in your case, for simplicity(*))
In recent versions, convert is replaced by magick or magick convert
So for instance, starting with:
And applying this 512-colors colormap
You obtain this:
Note that the color-reduced image can contain much less than the 556 colors (190 colors in the image above, despite the 512 colors colormap) (you won't have bright reds in Mona Lisa).
The whole thing is documented here.
After trying the process a few times, I find that given a good palette it works quite well, so if your 556 colors make up good palette, you could make your workflow a lot simpler, by working in full RGB all the time, and then converting the image to 556 colors.
(*) TIFF and WebP formats also support exact colors/lossless compression, but they still have variants that will do a JPEG-like compression that will change the colors, so they must be used with care.
Using ImageMagick or GhostScript or any PHP code how can I get the DPI value of PDF files?
Here is the link for two demo files
http://jmp.sh/O5g5wL4 -- of 72 DPI
http://jmp.sh/RxrnYrY -- of 300 DPI
I have used
$image = new Imagick();
$image->readImage('xyz.pdf');
$resolutions = $image->getImageResolution();
It gives the same result for two different PDF files having different DPI.
I have also used
pdfimages -list xyz.pdf
It gives a list of all information but how to fetch the DPI value from the list.
How to get the exact DPI value of a PDF?
As fmw42 says PDF files themselves have no resolution. However in your case both the files consist of nothing but an image. In one case the image is ~48 MB and in the other its around 200 MB.
The reason is that the images have a different effective resolution.
In PDF the image is simply a bitmap, a sequence of coloured pixels. These are then drawn onto the underlying media. At this point there is no resolution, the pixels are laid down in a specific media size. In your case 22 inches by 82 inches.
The effective resolution is given by dividing the dimension by the number of pixels in the image in that dimension.
So if I have an image which is 1000x1000 pixels, and I draw it in a 1 inch square, then the effective resolution of the image is 1000 dpi. If I change my mind and draw it in a square 4 inches by 4 inches, then the effective resolution is 250 dpi.
The image hasn't changed, just the area it covers.
Now consider I have two images drawn in 1 inch squares. the first image is 1000x1000, the second is 500x500. The effective resolution of the first image is 1000 dpi, the effective resolution of the second is 500 dpi.
So you can see that, in PDF, the effective resolution of the image is a combination of the dimensions of the image, and the dimensions of the media it covers.
That's a difficult thing to measure in a PDF file. The area covered is calculated using matrix algebra and can be a combination of several different matrices.
The actual dimensions of the image, by contrast are quite easy to determine, they are given in the image dictionary. Your images are: 1620x5868 and 3372x12225. In both cases the media is the same size; 22.5x81.5 inches.
Since the images cover the entire media, the effective resolutions are;
1620/22.5 = 72 by 5868/81.5 = 72
3372/22.5 = 149.866 by 12225/81.5 = 150
I think MuPDF will give you image dimensions and media dimensions, assuming all your PDF files are constructed like this you can then simply perform the maths, but note that this won't be so simple for ordinary PDF files where images don't cover the entire media.
Using mutool info -I -M 150-dpi.pdf gives:
Retrieving info from pages 1-1...
Mediaboxes (1):
1 (6 0 R): [ 0 0 1620 5868 ]
Images (1):
1 (6 0 R): [ DCT ] 3375x12225 8bpc DevCMYK (12 0 R)
So there's your image dimensions and your media size. All you need to do is apply the division of one by the other.
Note: In debian and related distros, mutool is contained in mupdf-tools package, not in mupdf package itself. It can by therefore installed by sudo apt install mupdf-tools.
I use pdfimages -list from the poppler library, gives you all the information about the images.
I've got a 8.5x11 PDF at 300dpi. It has a single UPC label in the top left corner of the PDF. Imagine that there could be 30 labels on a 1 sheet, but we just have 1 label.
I'm trying to crop the PDF to be just the size of the 1 label. So far I've got this
gm convert -density 300 single.pdf out.pdf
Which doesn't do any cropping. When I crop to say 300x100 it makes a 20MB file with 30000 pages.
I have not a clue how to use -crop to actually crop to the correct size. I need it to be 3.5inches by 1.125 inches.
Using the following input PDF (here converted to a PNG):
the following command will crop the label:
gm wiz.pdf -crop 180x50+1+1 cropped.pdf
This label is sized 180x50 pixels.
For an 8.5x11in PDF at 300 PPI you'd have a 2450x3300 pixels PDF (which I doubt you do, but that's another question) and you'd need to use -crop 1050x337+0+0 (more exactly, 1050x337.5+0+0 -- but you cannot crop half pixels!).
Note, the +0+0 part crops the top left corner. If you need offset to the right by N pixels and to the bottom by M pixels use +N+M...
Using ImageMagick instead...
You could also use ImageMagick's convert command:
convert wiz.pdf[180x50+1+1] cropped.pdf
Comment about image sizes...
One additional comment about this remark:
"I have not a clue how to use -crop to actually crop to the correct size."
There is no other real size for raster images than pixels. ABC pixels wide and XYZ pixels high...
There is no such thing as an absolute, real size for a digital image that you can measure in inches... unless you additionally can state the resolution at which a given image is rendered on a display or a print device!
An 8.50x11in sized image at 300 PPI will translate to 2550x3300 pixels.
However, if your image does not contain this amount of pixels (which is the real, absolute size of any raster image), you may still be able to render it at 300 PPI -- but its size in inches will be different from 8.5x11in!
So, whenever you want to crop, use the absolute number of pixels you want. Don't use resolution/density at all on your command line!
I have many scanned document in PDF.
I use ImageMagick with Ghostscript to convert PDF to PNG in big density. I use convert -density 288 2.pdf 2.png. After that I read the pixels with PHP and find where is QR code and decode it. Because image is very big (~ 2500px), it's need very much RAM. I want, before I read pixels with PHP, to crop the image with ImageMagick and leave only that part with the QR code.
Can I detect the approximate location of QR code with ImageMagick, crop and leave only that part ?
Sample PDF
Converted PNG
Further Update
I see your discussion with Kurt about better extraction of the image from the PDF in the first place, and his recommendation was to use pdfimages. I just wanted to add that you won't find that if you do brew search pdfimages, but you actually need to use
brew install poppler
and then you get the pdfimages executable.
Updated Answer
If you change the tile size to 100x100 on the crop command and run this for the second PDF you supplied:
convert -density 288 pdf2.pdf -crop 100x100 tile%04d.png
and then use the same entropy analysis command
convert -format "%[entropy]:%X%Y:%f\n" tile*.png info: | sort -n
...
...
0.84432:+600+3100:tile0750.png
0.846019:+600+2800:tile0678.png
0.980938:+700+400:tile0103.png
0.984906:+700+500:tile0127.png
0.988808:+600+400:tile0102.png
0.998365:+600+500:tile0126.png
The last 4 listed tiles are
Likewise for the other PDF file you supplied, you get
0.863498:+1900+500:tile0139.png
0.954581:+2000+500:tile0140.png
0.974077:+1900+600:tile0163.png
0.97671:+2000+600:tile0164.png
which means these tiles
I would think that should help you pretty much approximately locate the QR code.
Original Answer
This is not all that scientific, but it may help you get started. The key, I think, is the entropy of the various areas of the image. The QR code has a lot of information encoded in a small area so it should have high entropy. So, I use ImageMagick to split the image into square 400x400 tiles like this:
convert image.png -crop 400x400 tile%03d.png
which gives me 54 tiles. Then I calculate the entropy of each of the tiles and sort them by increasing entropy, also outputting their offsets from the top left of the frame, and their name, like this:
convert -format "%[entropy]:%X%Y:%f\n" tile*.png info: | sort -n
0.00408949:+1200+2800:tile045.png
0.00473755:+1600+2800:tile046.png
0.00944815:+800+2800:tile044.png
0.0142171:+1200+3200:tile051.png
0.0143607:+1600+3200:tile052.png
0.0341039:+400+2800:tile043.png
0.0349564:+800+3200:tile050.png
0.0359226:+800+0:tile002.png
0.0549334:+800+400:tile008.png
0.0556793:+400+3200:tile049.png
0.0589632:+400+0:tile001.png
0.0649078:+1200+0:tile003.png
0.10811:+1200+400:tile009.png
0.116287:+2000+3200:tile053.png
0.120092:+800+800:tile014.png
0.12454:+0+2800:tile042.png
0.125963:+1600+0:tile004.png
0.128795:+800+1200:tile020.png
0.133506:+0+400:tile006.png
0.139894:+1600+400:tile010.png
0.143205:+2000+2800:tile047.png
0.144552:+400+2400:tile037.png
0.153143:+0+0:tile000.png
0.154167:+400+400:tile007.png
0.173786:+0+2400:tile036.png
0.17545:+400+1600:tile025.png
0.193964:+2000+400:tile011.png
0.209993:+0+3200:tile048.png
0.211954:+1200+800:tile015.png
0.215337:+400+2000:tile031.png
0.218159:+800+1600:tile026.png
0.230095:+2000+1200:tile023.png
0.237791:+2000+0:tile005.png
0.239336:+2000+1600:tile029.png
0.24275:+800+2400:tile038.png
0.244751:+0+2000:tile030.png
0.254958:+800+2000:tile032.png
0.271722:+2000+2000:tile035.png
0.275329:+0+1600:tile024.png
0.278992:+2000+800:tile017.png
0.282241:+400+1200:tile019.png
0.285228:+1200+1200:tile021.png
0.290524:+400+800:tile013.png
0.320734:+0+800:tile012.png
0.330168:+1600+2000:tile034.png
0.360795:+1200+2000:tile033.png
0.391519:+0+1200:tile018.png
0.421396:+1200+1600:tile027.png
0.421421:+2000+2400:tile041.png
0.421696:+1600+2400:tile040.png
0.486866:+1600+1600:tile028.png
0.489479:+1600+800:tile016.png
0.611449:+1600+1200:tile022.png
0.674079:+1200+2400:tile039.png
and, hey presto, the last one listed (i.e. the one with the highest entropy) tile039.png is this one.
I have drawn a rectangle around its location using this command
convert image.png -stroke red -fill none -strokewidth 3 -draw "rectangle 1200,2400 1600,2800" a.jpg
I concede there may be luck involved, but I only have one image to test my mad theories. You may need to tile twice, the second time with an x-offset and y-offset of half a tile width, so that you don't cut the QR code and split it across 2 tiles. You may need different size tiles for different size barcodes. You may need to consider the last 3-5 tiles located for your next algorithm. But I think it could form the basis of a method.
The goal is to validate an image based on dynamic height and width parameters, as well as DPI.
ImageMagick has the following command Identify which has a number of options.
-density
will generate the geometry widthxheight
-verbose
will generate a helpful "Print size: " and "Resolution"... among 78 other different lines... where width and height need to be parsed out to meet minimum requirements +/- 2%
so how does one extract those into a method, without stepping on intermediate toes (mini-magick)?
As the section on meta-information indicates, MiniMagick accesses the data using ImageMagick function in a single call, for example height density:
image["%y"]
ImageMagick has 47 single-letter attribute percent escapes that allows extraction of the data, provided your call to the image contains a ".path" suffix
image = MiniMagick::Image.open(#yourClass.theColumn.path)