I have the following image 188_f.jpg:
And the following code:
<?php
$ss = "convert 188_f.jpg -quality 95% -set colorspace RGB -colorspace CMYK 188_f_cmyk.jpg 2>&1";
echo ">" . $ss . "<br />";
echo system($ss);
?>
When I run this code, I get this image as output:
Which is indeed in CMYK, but when viewed at 100% there is a significant loss in quality. (Wasn't sure if SE did any conversions when uploading, so I uploaded the above images via FTP so you can examine them directly if needed.)
I tried moving the quality argument around, with and without the percent sign, and I also looked through the Imagick guide, but I couldn't find any explanation for why the quality goes down. The output file has the same number of pixels.
EDIT: Making no other changes to the script except changing the colorspace options, here were the results:
EDIT 2: Also tried multiple different profiles, using this:
convert 188_f.jpg -quality 95% -profile profiles\\UncoatedFOGRA29.icc -colorspace CMYK 188_f_cmyk.jpg 2>&
None of them got rid of the pixelatedness.
I managed to get an output indistinguishable from your original image with the following options passed either to convert or mogrify:
-filter Triangle -define filter:support=2 -unsharp 0.25x0.25+8+0.065 -dither None -posterize 136 -quality 82 -define jpeg:fancy-upsampling=off -interlace none -colorspace sRGB -strip
(ref: https://www.smashingmagazine.com/2015/06/efficient-image-resizing-with-imagemagick/)
(left: original - 74.8kB, right: converted - 63kB)
Related
a) I have multiple ImageMagick commands and I need to convert those multiple commands into one. I tried it by putting all the parameters in single command, but somehow it was not working and I had to discard it.
magick -density 300 cheque25.jpg -depth 8 -strip -background white -alpha off cheque25.png
magick convert cheque25.png -resize 150% res_cheque25.png
magick convert -brightness-contrast 10x30 res_cheque25.png b_res_cheque25.png
magick convert b_res_cheque25.png -threshold 45% bin_res_cheque25.png
b) Also, is there any chance that merged commands will give any different output than multiple single command?
Your ImageMagick syntax is not correct in several ways. In ImageMagick 7, you replace convert with magick. Also your input should come right after magick. ImageMagick 6 is forgiving of syntax, but ImageMagick 7 is not. See http://imagemagick.org/script/porting.php#cli
Try the following:
magick cheque25.jpg -depth 8 -strip -alpha off -background white -resize 150% -brightness-contrast 10x30 -threshold 45% -density 300 bin_res_cheque25.png
If that does not work, then provide a link to your input image, so others can test your commands and verify against mine.
The combined commands should give the same as a properly formatted set of commands, provided no syntax errors are present and settings are reset where needed and parenthesis processing is properly used when and where needed. I make no guarantees, since your set of commands is not using proper syntax.
I was able to convert my EXR image to a PNG using the techniques outlined in Image conversion from IFF and EXR formats to JPEG format .
convert 0007.exr /tmp/0007.png
Unfortunately the PNG looks quite dim.
What should I add to the imagemagick convert command line to increase the brightness?
Starting with this:
You could try -auto-gamma:
convert start.jpg -auto-gamma result.jpg
If the -auto-gamma overcooks the image for your liking, you could apply a percentage of it. So, here I clone the original image and apply auto-gamma to the clone but then only blend 80% back into the original because I feel auto-gamma overdoes it:
convert start.jpg \( +clone -auto-gamma \) \
-define compose:args=80 -compose blend -composite result.jpg
Or, another option, you could experiment with your particular images and maybe try using -modulate for the brightness, where 100% means "do nothing", so numbers over 100 increase the brightness:
convert start.jpg -define modulate:colorspace=LCHuv -modulate 160 result.jpg
You can try -auto-level, which will take the minimal value and the maximal value of your picture and then stretches the values to the full range of values:
convert input.exr -auto-level output.jpg
Note that if you picture was too bright and this does not help, then it might be that your image is stored with 32 Bit, while ImageMagick is working with 16 Bit and no HDRI support. 32 Bit input is supported if convert --version
either show Q32 as part of the version string or lists HDRI under features.
Depending on your operating system you might be able to install another variant of ImageMagick. For example, for Debian Buster we can use sudo apt list imagemagick* to see that the package imagemagick-6.q16hdri is available. Installing this package provides convert-im6.q16hdri, which allows reading 32 Bit EXR images.
EXR is in linear RGB colorspace. You want to convert it to non-linear sRGB colorspace in Imagemagick as:
Input:
convert image.exr -set colorspace RGB -colorspace sRGB output.png
To solve Android build issue I need to replace all intermediate alpha pixel with solid pixel (leaving transparent background as is).
How to that with ImageMagick or other-command line tool to all images in a tree?
Image bg_all_block.9.png
Image btn_bg_common_press.9.png
UPDATE: I have found that I can detect if alpha is used, as in Detect Alpha Channel with ImageMagick
Other found links
https://graphicdesign.stackexchange.com/questions/16120/batch-replacing-color-with-transparency
http://www.imagemagick.org/Usage/color_basics/#replace
To remove the alpha channel from single image use this command:
convert input.png -alpha off output.png
To remove the alpha channel from all images inside a folder, make use find to first find all PNG files, and then run 'm through convert:
find . -name "*.png" -exec convert "{}" -alpha off "{}" \;
Please test on a COPY of your files to be sure.
...
see dialog below, and the answer is based on that "we need to remove alpha that is not 255"
convert input.png -channel A -threshold 254 output.png
and for batch
mkdir batch
FOR %G IN (*.png) DO convert %G -channel A -threshold 254 batch\%G
What worked for me on macOS for batch processing was:
for f in *.png; do convert "$f" -channel A -threshold 254 "${f%%.png}.png"; done
To remove alpha channel from all pictures in the folder (f.ex. all .png files) I use following command (in terminal on macOS):
for file in *.png; do convert $file -alpha deactivate; done
Unfortunately, none of any other solution given in this thread worked for me.
I am converting various PDFs uploaded by end users into images using following command
-density 140 -limit memory 64MB -limit map 128MB [pdffile] page.png
Here is the result. On the right we have original PDF and on the left output image. As you can see the colors are quite noticeably different.
What could be causing this and how fix it?
try following command:
-density 140 -limit memory 64MB -limit map 128MB -colorspace RGB [pdffile] page.png
Edit: I later discovered that ImageMagick can do it fine, I just needed to use -colorspace sRGB
My final command was:
convert -density 560 -limit memory 64MB -limit map 128MB \
-colorspace sRGB [pdffile] -scale 25% page.png
The oversampling and scaling down was to counter the poor anti-aliasing mentioned below.
Before I discovered that, here was my earlier solution...
In my case the colors produced by ImageMagick's convert were oversaturated, quite like those in the question. I was trying to convert this file using IM 6.7.7.10-6ubuntu3.
-resample 100 made no difference.
-colorspace RGB seemed to produce more accurate saturations, but the entire image was darker than it should have been.
Curiously, this suggestion to use GhostScript instead of ImageMagick for the conversion, produced very close to the correct colors:
gs -q -sDEVICE=png16m -dSubsetFonts=true -dEmbedAllFonts=true \
-sOutputFile=page.png -r200 -dBATCH -dNOPAUSE [pdffile]
(The original suggestion passed the -dUseCIEColor option, but in my case this appeared to reduce the gamma: light pixels were fine, but the dark pixels were too dark, so I removed it.)
After that, the only thing that bothered me was that the anti-aliasing/edges were a little off in places (especially visible on curves passing 45 degrees). To improve that, I created the output at four times the required resolution, and then scaled down afterwards, rendering those errors almost imperceptible. Note that I had to use ImageMagick's -scale for this, and not -geometry or -resize, in order to avoid bicubic ringing effects.
Use the -resample option:
-density 140 -resample 100 -limit memory 64MB -limit map 128MB [pdffile] page.png
Open Source MuPDF util mutool retains color and size using default parameters below
you need though to list the pages separated by a comma at the end of the command.
mutool draw -o draw%d.png abook.pdf 1,2
Otherwise if using Linux try Windows for better colorspace RGB interpretation when using imagemagick's convert.
The following images show how anti-aliasing improves if you sample at a higher resolution and then scale down.
Although 1120 was slightly better quality than 560, it took a long time to convert, so I would probably choose 560 for a good time:quality trade-off.
-colorspace sRGB -density 140
-colorspace sRGB -density 280 -scale 50%
-colorspace sRGB -density 420 -scale 33.3333%
-colorspace sRGB -density 560 -scale 25%
-colorspace sRGB -density 1120 -scale 12.5%
(It is easier to see the difference if you download the last two images and flip between them in your favourite image viewer. Or scroll up this list of images, instead of down. You should seem them becoming progressively uglier.)
I want to compress a JPG image file with ImageMagick but can't get much difference in size. By default the output size is bigger than the input. I don't know why, but after adding some +profile options and setting down the quality I can get an smaller size but still similar to original.
The input image is 255kb, the processed image is 264kb (using +profile to remove profiles and setting quality to 70%). Is there any way to compress that image to 150kb at least? Is that possible? What ImageMagick options can I use?
I use always:
quality in 85
progressive (comprobed compression)
a very tiny gausssian blur to optimize the size (0.05 or 0.5 of radius) depends on the quality and size of the picture, this notably optimizes the size of the jpeg.
Strip any comment or EXIF metadata
in imagemagick should be
convert -strip -interlace Plane -gaussian-blur 0.05 -quality 85% source.jpg result.jpg
or in the newer version:
magick source.jpg -strip -interlace Plane -gaussian-blur 0.05 -quality 85% result.jpg
Source.
From #Fordi in the comments (Don't forget to upvote him if you like this):
If you dislike blurring, use -sampling-factor 4:2:0 instead. What this does is reduce the chroma channel's resolution to half, without messing with the luminance resolution that your eyes latch onto. If you want better fidelity in the conversion, you can get a slight improvement without an increase in filesize by specifying -define jpeg:dct-method=float - that is, use the more accurate floating point discrete cosine transform, rather than the default fast integer version.
I'm using the Google Pagespeed Insights image optimization guidelines, and for ImageMagick they recommend the following:
-sampling-factor 4:2:0
-strip
-quality 85 [it can vary, I use range 60-80, lower number here means smaller file]
-interlace
-colorspace RGB
Command in ImageMagick:
convert image.jpg -sampling-factor 4:2:0 -strip -quality 85 -interlace JPEG -colorspace RGB image_converted.jpg
With these options I get up to 40% savings in JPEG size without much visible loss.
Just saying for those who using Imagick class in PHP:
$im -> gaussianBlurImage(0.8, 10); //blur
$im -> setImageCompressionQuality(85); //set compress quality to 85
Once I needed to resize photos from camera for developing:
Original filesize: 2800 kB
Resolution: 3264x2448
Command:
mogrify -quality "97%" -resize 2048x2048 -filter Lanczos -interlace Plane -gaussian-blur 0.05
Result filesize 753 kB
Resolution 2048x2048
and I can't see any changes in full screen with my 1920x1080 resolution monitor. 2048 resolution is the best for developing 10 cm photos at maximum quality of 360 dpi. I don't want to strip it.
edit: I noticed that I even get much better results without blurring. Without blurring filesize is 50% of original, but quality is better (when zooming).
#JavisPerez -- Is there any way to compress that image to 150kb at least? Is that
possible? What ImageMagick options can I use?
See the following links where there is an option in ImageMagick to specify the desired output file size for writing to JPG files.
http://www.imagemagick.org/Usage/formats/#jpg_write
http://www.imagemagick.org/script/command-line-options.php#define
-define jpeg:extent={size}
As of IM v6.5.8-2 you can specify a maximum output filesize for the JPEG image. The size is specified with a suffix. For example "400kb".
convert image.jpg -define jpeg:extent=150kb result.jpg
You will lose some quality by decompressing and recompressing in addition to any loss due to lowering -quality value from the input.
I would add an useful side note and a general suggestion to minimize JPG and PNG.
First of all, ImageMagick reads (or better "guess"...) the input jpeg compression level and so if you don't add -quality NN at all, the output should use the same level as input. Sometimes could be an important feature. Otherwise the default level is -quality 92 (see www.imagemagick.org)
The suggestion is about a really awesome free tool ImageOptim, also for batch process.
You can get smaller jpgs (and pngs as well, especially after the use of the free ImageAlpha [not batch process] or the free Pngyu if you need batch process).
Not only, these tools are for Mac and Win and as Command Line (I suggest installing using Brew and then searching in Brew formulas).
I added -adaptive-resize 60% to the suggested command, but with -quality 60%.
convert -strip -interlace Plane -gaussian-blur 0.05 -quality 60% -adaptive-resize 60% img_original.jpg img_resize.jpg
These were my results
img_original.jpg = 13,913KB
img_resized.jpg = 845KB
I'm not sure if that conversion destroys my image too much, but I honestly didn't think my conversion looked like crap. It was a wide angle panorama and I didn't care for meticulous obstruction.
Here's a complete solution for those using Imagick in PHP:
$im = new \Imagick($filePath);
$im->setImageCompression(\Imagick::COMPRESSION_JPEG);
$im->setImageCompressionQuality(85);
$im->stripImage();
$im->setInterlaceScheme(\Imagick::INTERLACE_PLANE);
// Try between 0 or 5 radius. If you find radius of 5
// produces too blurry pictures decrease to 0 until you
// find a good balance between size and quality.
$im->gaussianBlurImage(0.05, 5);
// Include this part if you also want to specify a maximum size for the images
$size = $im->getImageGeometry();
$maxWidth = 1920;
$maxHeight = 1080;
// ----------
// | |
// ----------
if($size['width'] >= $size['height']){
if($size['width'] > $maxWidth){
$im->resizeImage($maxWidth, 0, \Imagick::FILTER_LANCZOS, 1);
}
}
// ------
// | |
// | |
// | |
// | |
// ------
else{
if($size['height'] > $maxHeight){
$im->resizeImage(0, $maxHeight, \Imagick::FILTER_LANCZOS, 1);
}
}
Did some experimenting myself here and boy does that Gaussian blur make a nice different. The final command I used was:
mogrify * -sampling-factor 4:2:0 -strip -quality 88 -interlace Plane -define jpeg:dct-method=float -colorspace RGB -gaussian-blur 0.05
Without the Gaussian blur at 0.05 it was around 261kb, with it it was around 171KB for the image I was testing on. The visual difference on a 1440p monitor with a large complex image is not noticeable until you zoom way way in.
An very old but helpful answer.
I need to say, to serious large photography, -gaussian-blur is not acceptable, rather than compress ratio.
Comparing below, %95 with -gaussian-blur 0.05 vs. %85 without blurring. Original 17.5MB (8MP with much defail), %95 without blurring 5MB, %85 without blurring 3036KB, %95 with blurring 3365KB.
Comparing between blurring and compress ratio
Maybe lower blurring like 0.02 will work better.
If the image has big dimenssions is hard to get good results without resizing, below is a 60 percent resizing which for most of the purposes doesn't destroys too much of the image.
I use this with good result for gray-scale images (I convert from PNG):
ls ./*.png | xargs -L1 -I {} convert {} -strip -interlace JPEG -sampling-factor 4:2:0 -adaptive-resize 60% -gaussian-blur 0.05 -colorspace Gray -quality 20 {}.jpg
I use this for scanned B&W pages get them to gray-scale images (the extra arguments cleans shadows from previous pages):
ls ./*.png | xargs -L1 -I {} convert {} -strip -interlace JPEG -sampling-factor 4:2:0 -adaptive-resize 60% -gaussian-blur 0.05 -colorspace Gray -quality 20 -density 300 -fill white -fuzz 40% +opaque "#000000" -density 300 {}.jpg
I use this for color images:
ls ./*.png | xargs -L1 -I {} convert {} -strip -interlace JPEG -sampling-factor 4:2:0 -adaptive-resize 60% -gaussian-blur 0.05 -colorspace RGB -quality 20 {}.jpg