I have some PNG images with transparency. However, whenever I do any operations with ImageMagick on the image (e.g. cropping), it changes some of the images to be "indexed" color instead of RGB. The images that change are ones where there happens to be fewer than 256 colors, but the conversion ruins the transparency.
From some research I found you can prepend a filename with png32: to force RGB, but that only works when using the convert command, not mogrify.
I can add -format png32 with mogrify, but that renames all the images to *.png32.
Supposedly you can do this:
mogrify -define png:format=png32 -format png *.png
But it doesn't work, the images are still indexed color not RGB. How do I force PNG32 with mogrify?
Your command should have worked, if you are using a recent version of ImageMagick (6.9.1-3 or later).
Earlier versions will work if you use the -format png32 option as you did, then run a script to rename them back to *.png.
According to the ImageMagick 6 change log, the "-define png:format=png32" option was added to ImageMagick at version 6.7.3-0, but a bug was introduced at version 6.8.9-0 that caused it to be ignored in certain circumstances; that bug was fixed in version 6.9.1-3.
So the answer to your question is to either work around the problem by letting mogrify rename your input files to *.png32, or to upgrade your ImageMagick to 6.9.1-3 or later.
Related
I wanted to batch-convert some JPG images to PNG, so I used the following ImageMagick command:
convert before.jpg after.png
However, things didn't go as smooth as I planned. See two images below - first is before.jpg, second is after.png:
You can see that the second one is quite darker than the original.
I'm using ImageMagick 6.9.9-19.
Opening JPEG image in GIMP and exporting it as PNG gives expected result - output image is identical to original.
What am I doing wrong?
Edit: re-saving after.png with GIMP also makes the image identical to original.
Edit: even after I saved after.png with GIMP, re-converting with ImageMagick breaks colors again (convert after-gimp.png after-gimp-and-im.png).
Edit: converting to sRGB or CMYK TIFF, or even again to JPG, does not give this problem. However, I still need PNG.
The two images you posted are identical according to IM 6.9.9.20 Q16 Mac OSX compare -metric rmse GBooF.jpg geDxn.png null: Which produces: 0 (0). It is possible your viewers may display jpg and png differently, since neither have an sRGB profile. Though, png is usually assumed to be sRGB.
Also my viewer shows both of your images as the same --- no difference, in your post on Mac Safari and using Mac Preview.
Try adding an sRGB profile to your jpg. Then convert.
convert GBooF.jpg -profile path2/sRGB.icc GBooF2.jpg
convert GBooF2.jpg GBooF2.png
See if those view the same.
I'm trying to convert an not-optimized PNG to an optimized version using ImageMagick's convert command:
convert -colors 40 test.png test-optimized.png
The problem is however that the convert operation adds weird noise. I want multiple levels of alpha transparency in my export, which convert seems to offer, but without all the noise, and the file size should stay low. I wouldn't expect to need more than 16 different colors to optimize the original image with some levels of anti-aliasing in both the blue area and the transparent area. Any idea's? It almost looks like it is adding something like a JPEG compression or something (which of course doesn't add transparency). I tried already with different -anti-aliasing and -alpha options.
Source
Optimized
This question can be closed: the problem was a version issue.
The problem occurs with:
ImageMagick 6.9.0-0 (as reported by Mark Scetchell in the comments)
ImageMagick 6.9.1-0 Q16 x86_64 2015-04-06
But no longer with:
ImageMagick 6.9.3-0 Q16 x86_64 2016-01-31
Thanks to Mark Scetchel and Glenn Randers-Pehrson for their input.
I am using ImageMagick 6.7.7 on Ubuntu 14.04.2.
I am converting an RGB PDF to CMYK PDF and it looks dark. But it is working fine with ImageMagick 6.6.6.
I am using below command:
convert tp_rgb.pdf -verbose -density 300 -colorspace CMYK tp_cmyk.pdf
How can we fix that? Can any help me with this?
At version 6.7.6, ImageMagick started treating grayscale images without colorspace information as "linear" instead of "sRGB" by default, with the result that they looked darker. Later, the default was switched back to "sRGB" and a few related problems were fixed. Upgrading to version 6.8.9 or later will restore the original, expected behavior, where all images are handled as "sRGB" by default.
I want to convert multi page pdfs into single page images efficiently.
I already know how to do this one page at a time with imagemagick. For example,
convert x.pdf[2] x3.jpg
will give me the 3rd page of the pdf as an image. So if I figure out how many pages are in the pdf using identify then I can loop through and convert all pages in the pdf to images. This method can however take a while. For example a 15 page pdf could take anywhere between 15-30 seconds.
According to answers that I have seen elsewhere (also on the imagemagick forums) the following imagemagick command should split a pdf into multiple images.
convert x.pdf x-%0d.jpg
but all this ends up doing is creating the first page named x-0.jpg
As an alternative I have tried using pdftk with the burst capability. The problem I faced there is that burst does not work in all cases. It does for some pdf's and does not for some others.
Any suggestions on how to improve things would help.
My OS is Mac OSX Lion but I do need this working on CentOS 6 as well.
You're missing the quantity of digits. Use:
convert x.pdf x-%04d.jpg
Where 4 means 4 digits will be show on the page count.
If you use Graphicsmagick on Debian or ImageMagick on macOS you probably have to add ADJOIN to your command.
So it should look like
convert x.pdf +adjoin x-%04d.jpg
When I tried to convert my multi-page pdf, the resulting image files had a gray background despite the pdf having a white background. (#John P commented on it on the accepted answer, but I couldn't get his comment to directly work for me.)
Here's what worked for me to make the background white:
convert -authenticate yourpassword -background white -alpha remove -alpha off -density 300 -quality 80 -verbose "Your file.pdf" "Your file.png"
My pdf had a password hence the authenticate.
You can see a summary of the options here:
-authenticate value decipher image with this password
-background color background color
-alpha on, activate, off, deactivate, set, opaque, copy", transparent, extract, background, or shape the alpha channel
-density geometry horizontal and vertical density of the image
-quality value JPEG/MIFF/PNG compression level
-verbose print detailed information about the image
More detail: https://imagemagick.org/script/convert.php
And the alpha remove option: http://www.imagemagick.org/Usage/masking/#alpha_remove
Ran into the same issue. Reinstall Imagemagick to work in Mountain Lion. If you use brew the simply
$brew unlink imagemagick
$brew install imagemagick
I'm using ImageMagick to convert PDF files to PNGs. (Lots of text, so I'd rather use PNG over JPEG.) I'm doing this on OS X, 10.8.2.
I tried using Ghostscript, then ImageMagick, as was done here and I got a gray background. I shortened it to one line, since ImageMagick can work with PDFs and tried this:
convert -background transparent -transparent white \
Background-Page01.pdf TestClearX1.png
I've tried that with PNG files and JPEG files. (And with and without -transparent white as well.)
If it's a JPEG, I can get a white background (which is probably clear, but in my viewer, I can't tell), but with a PNG, I always get a dark background. I thought about, as a test, trying to generate a BMP, then converting that to PNG, but it won't generate BMP files.
How can I get a transparent background for a PNG file?
And if that's not possible, since JPEG files are not good for text, is there a better alternative?
This isn't an answer, but the format of the comment section doesn't allow sensible formatting, so I am offering it here instead.
You alluded to the fact that Preview in OS X doesn't show transparency properly, and that is correct. To get around that, I made the following script, which overlays the files you want to view onto a checkerboard pattern like Photoshop does. I save it as preview and then use chmod +x preview on it to make it executable. Here is the script:
#!/bin/bash
################################################################################
# preview
# Preview images using OSX "open" but overlay images on top of checkerboard
# first so you can see transparency/transparent pixels, since Preview renders
# them grey :-(
################################################################################
for f in "$#"
do
base=$(basename "$f")
composite -compose Dst_Over -tile pattern:checkerboard "$f" "/tmp/$base"
open -g "/tmp/$base"
done
That enables you to do:
/.preview file1.png file2.gif
and the -g option also means Preview doesn't steal focus too :-)
So, instead of looking like this:
it looks like this:
There's two ways to export a PDF in LibreOffice, and one way does not provide any warnings. The other way provides a warning that PDF/A cannot have transparent objects. The problem is you're using PDF/A files that don't support transparent objects—this results in your PNG always having a background colour.