I have a small pixel map and want to resize it for better readability.
Using mogrify -resize 1600% I get an interpolated image: .
What I'm trying to get is this: .
Can this be done by ImageMagick or any other open source command line tool?
I finally found the solution: using -scale instead of -resize does the trick. It is 'hidden' under the heading Scale - Minify with pixel averaging, therefore I overlooked it at first, searching for magnification instead of minification.
This worked for me:
convert input.png -interpolate Integer -filter point -resize "10000%" output.png
Explanation:
Interpolation method "Integer" just picks a nearest value.
Filter 'point' is also necessary, but I do not know why.
display -sample 400% worked for me.
"Change the image size simply by directly sampling the pixels original from the image. When magnifying, pixels are replicated in blocks. When minifying, pixels are sub-sampled (i.e., some rows and columns are skipped over)."
https://imagemagick.org/script/command-line-options.php#sample
To keep the original values of the input image and avoid any blend or bluriness, you can use -interpolate nearest-neighbor or -interpolate integer.
It only works along -interpolative-resize. Be aware that -resize does not work correctly with -interpolate. You can check here on the imagemagick docs.
e.g.
convert input.png -interpolate nearest-neighbor -interpolative-resize 1600% output.png
Related
I have a PDF form that has a box like this:
I'm trying to run it through AWS Textract but it interprets the pipes in between the numbers. The pipes are actually like dark gray. So I hoped if I used Image Magick with a threshold I could get the number without the pipes but it's not working.
I tried this but any threshold amount doesn't help.
magick input.pdf -threshold 95% output.png
I'm trying to get something like this (which I did manually taking a screenshot and applying a threshold)
How can I achieve the above from the command line (or in Python)?
Just adjust your threshold lower in Imagemagick.
convert img.png -threshold 60% x.png
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.
I have a lot of PDF documents that I want to convert to PNG, edit in Gimp, and then save back to the multipage Acrobat file. I'm filling out forms and adding scanned signature, trying to avoid printing, signing, then scanning back in, with the ability to type the information I need to enter.
I've been trying to use Imagemagick to convert to png files, which seems to work fine. I use the command convert -quality 100 -density 300x300 multipage.pdf single%d.png
(I'm not really sure if the quality parameter is right for png).
But I'm having problems with saving back to PDF. Some of the files have the wrong page size, and I've tried every command and procedure I can find, but there are always a few odd sizes. The resolution seems to vary so that it looks good at a certain zoom level, but either a few pages are specified at about 2" wide, or they are 8.5x11 but the others are about 35" wide. I've tried making sure Gimp had the canvass size and resolution correct, and to save the resolution in the file, but that doesn't seem to matter.
The command I use to save the files is convert -page letter -adjoin single*.png multipage.pdf I've tried other parameters, but none seemed to matter.
If anyone has any ideas or alternatives, I'd appreciate it.
"I'm not really sure if the quality parameter is right for PNG."
For PNG output, the -quality setting is very unlike JPEG's quality setting (which simply is an integer from 0 to 100).
For PNG it is composed by two single digits:
The first digit (tens) is (largely) the zlib compression level, and it may go from 0 to 9.
(However the setting of 0 has a special meaning: when you use it you'll get Huffman compression, not zlib compression level 0. This is often better... Weird but true.)
The second digit is the PNG data encoding filter type (before it is compressed):
0 is none,
1 is "sub",
2 is "up",
3 is "average",
4 is "Paeth", and
5 is "adaptive".
In practical terms that means:
For illustrations with solid sequences of color a "none" filter (-quality 00) is typically the most appropriate.
For photos of natural landscapes an "adaptive" filtering (-quality 05) is generally the best.
"I'm having problems with saving back to PDF. Some of the files have the wrong page size, and I've tried every command and procedure I can find [...] but either a few pages are specified at about 2" wide, or they are 8.5x11 but the others are about 35" wide."
Not having available your PNG files, I created a few simple ones with different dimensions to verify the different commands (as I wasn't sure myself any more). Indeed, the one you used:
convert -page letter -adjoin single*.png multipage.pdf
does create all PDF pages in (same) letter size, but it places my sample of (differently sized) PNGs always on the lower left corner of the PDF page. (Should a PNG exceed the PDF page size, it does scale them down to make them fit -- but it doesn't scale up smaller PNGs to fill the available page space.)
The following modification to the command will place the PNGs into the center of each PDF page:
convert \
-page letter \
-adjoin \
single*.png \
-gravity center \
multipage.pdf
If this is still not good enough for you, you can enforce a (possibly non-proportional!) scaling to almost fill the letter area by adding a -scale '590!x770!' parameter (this will leave a border of 11 pt at each edge of the page):
convert \
-page letter \
-adjoin \
single*.png \
-gravity center \
-scale '590!x770!' \
multipage.pdf
To leave away the extra border, use -scale '612!x792!'. -- Should you want only upward scaling to happen if required while keeping the aspect ratio of the PNG, use -scale '590<x770<':
convert \
-page letter \
-adjoin \
single*.png \
-gravity center \
-scale '590<x770<' \
multipage.pdf
Why not just use Xournal? That's what I use to annotate PDFs
I have a camera which produces photographs of 3008x2000 pixels. I use Image Magick to scale and resize the photos to be put up on my website. The size of the images I am using on the website is 602x400. I use this command to reduce the size:
convert DSC_0124.JPG -scale 20% -size 24% img1.jpg
This produces an image which is 602x400 pixels in size. But the file size will be always above 250KB. More images on a single html page means the page will be heavier and loading time will be longer. Are there any features in image magic that will help me to keep the file size as small as possible, possibly, below 100KB. But the image size should be the same, that is, 602x400px. I have achieved similar optimisation with SEAMonster tool for MS Windows. As it doean't have a commandline alternative, it wouldn't be of much help when there are hundreds of images to be converted.
Use command as Delan proposed with additional "-strip" flag to remove EXIF data, this have reduced the size of some of my images drastically. Here is a bash script for unix platforms, but you can use the second part only for individual images.
for X in *.jpg; do convert "$X" -resize 602x400 -strip -quality 86 "$X"; done
This will convert all images in the directory.
Use -quality to set the compression level:
convert DSC_0124.JPG -scale 20% -size 24% -quality [0..100] img1.jpg
You can define the maximum size of the output image at 100KB like this:
convert DSC_0124.JPG -resize 602x400! -strip -define jpeg:extent=100KB img1.jpg
If you are running your website on PHP, you might want to consider the SLIR image resizing script, it does a great job resizing to various constraints (see below) and caches the results.
Parameters:
w Maximum width
h Maximum height
c Crop ratio
q Quality
b Background fill color
p Progressive
http://shiftingpixel.com/2008/03/03/smart-image-resizer/
http://code.google.com/p/smart-lencioni-image-resizer/
When I try to run a bunch of PNG-8 images with alpha transparency through Imagemagick, it converts them to PNG-32, increasing the file size a lot.
Is it possible to force Imagemagick to keep my image type as 8-bit PNG?
You can do it like this:
convert test.png PNG8:test2.png
I've had varying luck with IM and PNG8, but this is the correct way to do it.
I seem to get the best result using the following
convert src.png -colors 256 PNG8:dest.png