i have a little cocoa osXa app that uses Vips DZSAVE and imagemagick to create the DeepZoom Tile from a big psb file.
the problem is that it works fine just till a undefined size. i'm managing correctly files about 60.000px X 50.000px 27Gb size but whit bigger files the app is generating a tile made by white images.
No data are written...
i have to manage images around 170.000px X 170.000px between 60 and 80 Gb.
i have tried Environment Variables to increase imagemagick cache limits but, no results...
someone has some ideas about the white output?
I'm the vips maintainer. Try at the command-line, something like:
vips dzsave huge.psb output_name --tile-size 256 --overlap 0 --vips-progress --vips-leak
and see what happens. If you run "top" at the same time you can watch memory use.
vips uses libMagick to load the psb files and my guess would be that this is hitting a memory limit somewhere inside ImageMagick.
Do you have to use psb? If you can use a format that vips can process directly it should work much better. Big TIFF or Openslide (if these are slide images) are both good choices. I regularly process 200,000 x 200,000 images with dzsave on a very modest laptop.
I would like to split large pictures, but they are two big to be opened for my GPU. Max JPEG size i can completly open is over 35Mo and 150,000,000px, with any program tried, using almost all resources. Windows affords opening heavier images after resizing them, so actually there is no more difference between 20Mo and 200Mo pictures on screen. Usual image editors do not try to resize them but they get my computer crash. The only way i found to open completly and safely is into.. a browser.
I also found two useful websites for online splitting but none of them handles pictures larger than 20Mo.
how can one split an image when it is too large to be opened, even on specialized websites ?
Not sure why you would use Chrome or anything web-based, as your uncompressed image is going to require 3+GB of RAM to decompress and get started on.
I would use ImageMagick like this:
convert -crop 10x10# input.png +repage out%02d.png
that will get you 100 tiles, each 2,160 pixels square, called out00.png to out99.png
Using ffmpeg I can take a number of still images and turn them into a video. I would like to do this to decrease the total size of all my timelapse photos. But I would also like to extract the still images for use at a later date.
In order to use this method:
- I will need to correlate the original still image against a frame number in the video.
- And I will need to extract a thumbnail of a given frame number in a
video.
But before I go down this rabbit hole, I want to know if the requirements are possible using ffmpeg, and if so any hints on how to accomplish the task.
note: The still images are timelapse from a single camera over a day, so temporal compression will be measurable compared to a stack of jpegs.
When you use ffmpeg to create a video from a sequence of images, the images aren't affected in any way. You should still be able to use them for what you're trying to do, unless I'm misunderstanding your question.
Edit: You can use ffmpeg to create images from an existing video. I'm not sure how well it will work for your purposes, but the images are pretty high quality, if not the same as the originals. You'd have to play around with it to make sure the extracted images are exactly the same as the input images as far as sequential order and naming, but if you take fps into account, it should work.
The command to do this (from the ffmpeg documentation) is as follows:
ffmpeg -i movie.mpg movie%d.jpg
In my application I need to resize and make the quality on PNG files poorer.
In full size the PNGs are 3100x4400px using 2,20MB disk space.
When running the following command:
convert -resize 1400 -quality 10 input.png output.png
the images are resized to 1400x2000 using 5,33MB disk space.
So my question is: How can I reduce the file size?
You can further reduce quality of PNG by using posterization:
https://github.com/pornel/mediancut-posterizer (Mac GUI)
This is a lossy operation that allows zlib to compress better.
Convert image to PNG8 using pngquant.
It reduces images to 256 colors, so quality depends on the type of image, but pngquant makes very good palettes, so you might be surprised how often it works.
Use Zopfli-png or AdvPNG to re-compress images better.
This is lossless and recommended for all images if you have CPU cycles to spare.
After using imagemagick to resize, you can compress the image using pngquant.
On mac (with homebrew) brew install pngquant then:
pngquant <filename.png>
This will create a new image filename-fs8.png that is normally much smaller in size.
Help page says, that -quality option used with PNG sets the compression level for zlib, where (roughly) 0 is the worst compression, 100 - is the best (default is 75). So try to set -quality to 100 or even remove the option.
Another method is to specify PNG:compression-level=N, PNG:compression-strategy=N and PNG:compression-filter=N to achieve even better results.
http://www.imagemagick.org/script/command-line-options.php#quality
For lazy people that arrived here wanting to paste in a one liner:
mogrify -resize 50% -quality 50 *.png && pngquant *.png --ext .png --force
This modifies all of the pngs in the current directory in place, so make sure you have a backup. Modify your resize and quality parameters as suits your needs. I did a quick experiment and mogrify first, then pngquant, resulted in significantly smaller image size.
The ubuntu package for pngquant is called "pngquant" but I had it installed already on 20.04LTS so seems like it may be there by default.
I found that the best way was to use the
- density [value]
parameter.
Consider an application handling uploading of potentially very large PNG files.
All uploaded files must be stored to disk for later retrieval. However, the PNG files can be up to 30 MB in size, but disk storage limitations gives a maximum per file size of 1 MB.
The problem is to take an input PNG of file size up to 30 MB and produce an output PNG of file size below 1 MB.
This operation will obviously be lossy - and reduction in image quality, colors, etc is not a problem. However, one thing that must not be changed is the image dimension. Hence, an input file of dimension 800x600 must produce an output file of dimension 800x600.
The above requirements outlined above are strict and cannot be changed.
Using ImageMagick (or some other open source tool) how would you go about reducing the file size of input PNG-files of size ~30 MB to a maximum of 1 MB per file, without changing image dimensions?
PNG is not a lossy image format, so you would likely need to convert the image into another format-- most likely JPEG. JPEG has a settable "quality" factor-- you could simply keep reducing the quality factor until you got an image that was small enough. All of this can be done without changing the image resolution.
Obviously, depending on the image, the loss of visual quality may be substantial. JPEG does best for "true life" images, such as pictures from cameras. It does not do as well for logos, screen shots, or other images with "sharp" transitions from light to dark. (PNG, on the other hand, has the opposite behavior-- it's best for logos, etc.)
However, at 800x600, it likely will be very easy to get a JPEG down under 1MB. (I would be very surprised to see a 30MB file at those smallish dimensions.) In fact, even uncompressed, the image would only be around 1.4MB:
800 pixels * 600 pixels * 3 Bytes / color = 1,440,000 Bytes = 1.4MB
Therefore, you only need a 1.4:1 compression ratio to get the image down to 1MB. Depending on the type of image, the PNG compression may very well provide that level of compression. If not, JPEG almost certainly could-- JPEG compression ratios on the order of 10:1 are not uncommon. Again, the quality / size of the output will depend on the type of image.
Finally, while I have not used ImageMagick in a little while, I'm almost certain there are options to re-compress an image using a specific quality factor. Read through the docs, and start experimenting!
EDIT: Looks like it should, indeed, be pretty easy with ImageMagick. From the docs:
$magick> convert input.png -quality 75 output.jpg
Just keep playing with the quality value until you get a suitable output.
Your example is troublesome because a 30MB image at 800x600 resolution is storing 500 bits per pixel. Clearly wildly unrealistic. Please give us real numbers.
Meanwhile, the "cheap and cheerful" approach I would try would be as follows: scale the image down by a factor of 6, then scale it back up by a factor of 6, then run it through PNG compression. If you get lucky, you'll reduce image size by a factor of 36. If you get unlucky the savings will be more like 6.
pngtopng big.png | pnmscale -reduce 6 | pnmscale 6 | pnmtopng > big.png
If that's not enough you can toss a ppmquant in the middle (on the small image) to reduce the number of colors. (The examples are netpbm/pbmplus, which I have always found easier to understand than ImageMagick.)
To know whether such a solution is reasonable, we have to know the true numbers of your problem.
Also, if you are really going to throw away the information permanently, you are almost certainly better off using JPEG compression, which is designed to lose information reasonably gracefully. Is there some reason JPEG is not appropriate for your application?
Since the size of an image file is directly related to the image dimensions and the number of colours, you seem to have only one choice: reduce the number of colours.
And ~30MB down to 1MB is a very large reduction.
It would be difficult to achieve this ratio with a conversion to monochrome.
It depends a lot on what you want at the end, I often like to reduce the number of colors while perserving the size. In many many cases the reduced colors does not matter. Here is an example of reducing the colors to 254.
convert -colors 254 in.png out.png
You can try the pngquant utility. It is very simple to install and to use. And it can compress your PNGs a lot without visible quality loss.
Once you install it try something like this:
pngquant yourfile.png
pngquant --quality=0-70 yourfile.png
For my demo image (generated by imagemagick) the first command reduces 350KB to 110KB, and the second one reduces it to 65KB.
Step 1: Decrease the image to 1/16 of its original size.
Step 2: Decrease the amount of colors.
Step 3: Increase the size of the image back to its original size.
I know you want to preserve the pixel size, but can you reduce the pixel size and adjust the DPI stored with the image so that the display size is preserved? It depends on what client you'll be using to view the images, but most should observe it. If you are using the images on the web, then you can just set the pixel size of the <img> tag.
It depends on they type of image, is it a real life picture or computer generated image,
for real life images png will do very little it might even not compress at all, use jpg for those images, it the image has a limited number of different colors (it can have a 24 bit image depth but the number of unique images will be low) png can compress quite nicely.
png is basicly an implementation of zip for images so if a lot of pixels are the same you can have a rather nice compression ratio, if you need lossless compression don't do resizing.
use optipng it reduce size without loss
http://optipng.sourceforge.net/
Try ImageOptim https://imageoptim.com/mac it is free and open source
If you want to modify the image size in ubuntu, you can try "gimp".
I have tried couple of image editing apps in ubuntu and this seemed to be the best among them.
Installation:
Open terminal
Type: sudo apt install gimp-plugin-registry
Give admin password. You'll need net connection for this.
Once installed, open the image with GIMP image editor. Then go to: File > Export as > Click on 'Export' button
You will get a small window, where check box on "Show preview in image window". Once you check this option, you will get to see the current size of the file along with Quality level.
Adjust the quality level to increase/decrease the file size.
Once adjusting is done, click on 'Export' button finally to save the file.
Right click on the image. Select open with paint. Click on resize. Click on pixel and change the horizontal to 250 or 200.
That's the only thing. It is the fastest way for those who are using Windows XP or Windows 7.