I'm using a nice enough cms (locomotive(github)) to allow some non-tech savy users to upload pictures to the system. The program is able to resize and crop pictures to any given size.
Trouble is, Internet explorer doesn't know how to deal with CMYK-encoded images. The users of this app are not exactly tech-savy; asking them to transform their images from CMYK to RGB is not an option. I'd like to modify locomotive so that it does the change automatically. I've been trying this for some hours but had no luck so far.
This is what I have found:
Locomotive uses dragonfly to perform the resizing.
Concretely, it uses dragonfly's imagemagick module.
The file that defines how Dragonfly is used in locomotive can be found here.
There is also a dragonfly initializer file.
I have also found that what (think) I need is adding a -colorspace RGB option to the parameter sent to Imagemagick by Dragonfly. It doesn't look like Dragonfly provides an easy option to do that.
I've tried several things, the last one consisting on monkeypatching Dragonfly's Imagemagick Processor so that the -colorspace RGB option is always used. I've added this in locomotive's config/initializers/dragonfly.rb:
# locomotive's config/initializers/dragonfly.rb
# ... Locomotive's default initialization
module Dragonfly
module ImageMagick
class Processor
alias :old_convert :convert
def convert(temp_object, args='', format=nil)
args += ' -colorspace RGB' # force RGB in all thumbnails
old_convert(temp_object, args, format)
end
end
end
end
I was pretty sure that this should work, but unfortunately it doesn't. And I have run out of ideas. Can anyone help?
On the commandline, I sometimes need to add -type truecolor to make colorspace conversions work reliably:
convert cmyk.jpeg -colorspace rgb -type truecolor rgb.jpeg
Maybe you try to add it in your code as well?
From the related list to the right, might this SO answer help?
Properly converting a CMYK image to RGB with RMagick
Unfortunately there doesn't seem to be a straightforward way to do this with Dragonfly. I've given up.
Related
Edit July 7, 2017: Downgrading to ImageMagick 6.9.5 solved this problem, which may be Cygwin-specific. I still don't know the underlying cause.
I need to extract data via OCR from images in PDF reports published by Chicago Public Schools. An example PDF is here (NB: this link downloads the file automatically rather than opening it in the browser). Here's a sample image (from PDF page 11, print page 8), extracted with pdfimages -png version 0.52.0 on Cygwin:
I'd like to crop each bar into its own file and extract the text with OCR. But when I try this with ImageMagick (version 7.0.4-5 Q16 x86_64 2017-01-25 according to convert -version), using the command convert chart.png -crop 320x600+0+0 bar.png, I get this image, with horizontal lines that interfere with OCR:
Running pdfimages to extract to PPM format first and then converting to PNG while cropping gives the same result, as does round-trip converting the extracted images to SVG format with ImageMagick's rsvg delegate, and fiddling with the PNG alpha channel changes the line's colors from gray to white or black but doesn't eliminate them. I've found a workaround of round-trip converting extracted images through JPG (introducing ringing artifacts, which I hope are irrelevant). But I don't see why I should have to do this. Incidentally, ImageMagick introduces the lines to PNGs even if I run a null conversion convert chart.png chart.png, which ought to leave the image unchanged:
I have found other complaints that PDF software adds horizontal lines to images, but none of them exactly matches this problem. A discussion thread mentions that versions of the PDF standard somehow differ in their treatment of alpha channels, but my knowledge of graphics is too poor understand the discussion fully; besides, my images get horizontal lines added after they're extracted from the PDF, because of something internal to ImageMagick. Can anyone shed some light on the causes of the grey lines?
Using the latest ImageMagick 7.0.6.0 Q16 Mac OS X, I get a good result. As mentioned above by Bonzo, the correct syntax for IM 7 is magick rather than convert. The use of convert reverts to IM 6. Also do not use magick convert either.
magick chart.png -crop 320x600+0+0 +repage bar.png
If this does not work for you, then there must have been a bug in your older version of IM 7. So you should then upgrade.
Note also the +repage is needed to remove the virtual canvas
I have used MiniMagick to compress JPEG files.
With strip function, I want to get rid of EXIF from image. So, I do:
image = MiniMagick::Image.open("my_picture.jpg")
image.strip
image.write("my_picture_small.jpg")
but sometimes the size of my_picture_small.jpg is bigger than my_picture.jpg.
However, when I don't use the strip function, like
image = MiniMagick::Image.open("my_picture.jpg")
# image.strip
image.write("my_picture_small.jpg")
my_picture_small.jpg's size is smaller.
That situation happened with some picture deal with Photoshop and in my CentOS computer, but run well with my Macbook. I don't know why stripping some information led to more storage.
Can anyone explain it?
Have found that ImageMagick will recompress image even if it with any arguments, such as
convert image.jpg new_image.jpg
new_image.jpg will be different from image.jpg more or less. If image.jpg is from a phone or camera or a image processing tools, the degree of difference is also different.
So compress images with MiniMagick or Rmagick that use ImageMagick as there system support, just do convert -strip image.jpg new_image.jpg may led to a unexpected result, avoid to use MiniMagick command if there is no need to greatly compress file.
I've been trying to save 8-bit PNGs (PNG8) using RMagick (http://rmagick.rubyforge.org/) and ChunkyPNG (https://github.com/wvanbergen/chunky_png) but have been unable to do so.
However the only time I can get it to work on RMagick is if the ImageMagick installation is based on the QuantumDepth of 8 rather than the usual 16. It is not possible to change this setting on the fly - the installation of ImageMagick has to be compiled with this setting.
Also setting the depth to 8 when creating the image or prefixing a format type when saving have no effect.
ie. img.write('PNG8:image.png')
Anyway I've had a look at ChunkyPNG and I really prefer to use this over RMagick - simply because it is pure Ruby and doesnt depend on ImageMagick. I can't save a PNG8 using that too.
I have to convert the PNG to 8bit afterwards using a graphics program -
My questions:
Is there a way of saving 8bit PNGs properly like it does on ImageMagick Q8 on a machine with ImageMagick Q16 installed?
Can anyone provide pointers as to do my own 4-bit encoder in ChunkyPNG or know of a way to save PNG8 with it?
Thanks in advance..
What exactly do you mean by PNG8? 8-bit grayscale, 8-bit indexed color, 3x8 bit RGB or 4x8 bit RGBA? All of these color modes are supported by ChunkyPNG.
By default, ChunkyPNG tries to determine the best color mode to save your image. You can overwrite it by providing an options hash to the save method:
image.save('filename.png', color_mode: ChunkyPNG::COLOR_TRUECOLOR)
# Or: ChunkyPNG::COLOR_TRUECOLOR_ALPHA
image.to_blob(color_mode: ChunkyPNG::COLOR_INDEXED, bit_depth: 8)
More info: https://github.com/wvanbergen/chunky_png/wiki
What command or series of commands could I execute from the CLI to recursively traverse a directory tree and reduce the bit-depth of all PNG files within that tree from 24bpp to 16bpp? Commands should preserve the alpha layer and should not increase the file size of the PNGs - in fact a decrease would be preferable.
I have an OSX based system at my disposal and am familiar with the find command so am really more keen to to locate a suitable PNG utility command.
Install fink
Say "fink install imagemagick" (might be "ImageMagick")
"convert -depth 16 old/foo.png new/foo.png"
If that did what you want, wrap it in a find call and be happy. If not, say "convert -help" and RTF-ImageMagick-M. :)
Optional: "fink install pngcrush" and run that as a second pass after the convert pass.
AFAIK the only PNG format that supports the alpha layer is PNG-24; Reducing the PNG to another format may require specifying a transparent color in a CLUT, which will not give you the output you want.
From the feature list on PNG's website:
8- and 16-bit-per-sample (that is, 24- and 48-bit) truecolor support
full alpha transparency in 8- and 16-bit modes, not just simple on-off transparency like GIF
... which I read to mean that anything other than PNG-24 or PNG-48 does not support full alpha transparency.
I'm working on a Sidebar Gadget and cannot get my JPEGs to show up (PNGs work). When I try to open the file by itself in IE8 it doesn't work. Firefox, of course, can open it fine.
JPEG Details:
Dimensions: 1080X900
180 dpi
Bit depth 24
Color representation: uncalibrated
I've found some things talking about the images being compressed incorrectly (?) but I haven't been able to get it working...
Any clues?
IE8 drops support for CMYK JPEG and renders them as the infamous red X without so much as a warning.
If you have ImageMagick:
identify -verbose image.jpg
will show you the image colorspace. If it's CMYK, you can convert to RGB with:
convert broken.jpg -colorspace RGB fixed.jpg
If you need to do CMYK to RGB conversion on a whole batch of JPEG-images, this command may be helpful to you:
for i in *.jpg; do convert "$i" -colorspace RGB "$i"; done
PS: If you'd like to see what is going on, just add -verbose:
for i in *.jpg; do convert "$i" -colorspace RGB -verbose "$i"; done
I had a similar issue with IE8 not displaying two JPEG images. FF, Safari, Chrome all displayed them without complaint but IE acted as if the files were not there. I have no idea what was going on, but a quick image conversion to gif or png fixed the problem. Just another in a long line of confirmations that IE sucks.
Had similar problems with existing images, which will not show up in IE8.
Problem is, as converter42 says: CMYK-Images
Convert them to RGB colorspace and all is good
The Solution with the PNG is not the best, because PNG files can be MUUUCH larger than JPGS.
If you are using photoshop for creating the jpgs. Try the below.
Open the file and go to 'Image' menu
Go to Mode
Select RGB
Save and upload to server.
This should work.
Why are you dealing with the image at 180 dpi and not the 72dpi screen resolution? At screen resolution the image will be roughly double that size. Still, the size is manageable for any browser.
When creating a gadget, you should be using PNGs for all the elements of the gadgets. Are you having issues displaying JPEG photos?
Have you looked for the yellow bar at the top of IE that blocks certain suspicious content from being loaded (popups, activex, javascript, etc.)? If it appears, try telling it to "allow".
Lastly, what are you using to compress your images to JPEG?
EDIT: If you want to do batch conversion use the batch converter in photoshop or use the Actions panel to record the conversion process for a single image, then replay the action on an entire folder. Additionally, you can save this action to a "droplet" which is a small application containing the action that you can drop an image or folder on top to.
Alternatively, if you don't fell like learning Actions, XNView is an excellent image viewer and converter that supports something like 160 different image formats and can batch convert and batch rename huge lists of files.
I fixed this issue by opening the CMYK JPEG file in Windows Paint and then saving as a JPEG, which Paint encodes as RGB by default. Not a great solution because I'm sure that Paint's converter is not as robust as Photoshop's, but this can be a quick fix if the job needs to be done now and there's no access to the tools above.