I'm working on a PHP script that automatically converts TIFF images to PNG files.
For that purpose, I use ImageMagick:
$ convert a.tif a.png
It works to some degree, however, the colours are very acute and deviant from the way they are pictured on my PC. To illustrate the problem, please have a look at the enclosed files, the include:
The Windows Live Foto Gallery output (that's pretty much how I want it to be)
The ImageMagick output (the mess I end up with)
The original TIFF file
Has anyone an idea whether, and if so how, I can alter the ImageMagick colour interpretation?
Thanks a lot!
Alright,
thanks to ergosys, the problem was easily solved: I needed to apply ICC colour profiles.
The XMP declared ISO 12647-2:2004, which was to be found at http://eci.org.
$ convert -profile ISOcoated_v2_eci.icc -profile eciRGB_v2.icc a.tif c.png
When converting from a CMYK color space to an RGB color space, as you do when going from tiff to png, you have to convert the color spaces along with the image. Try:
convert -colorspace rgb a.tif a.png
I ran this locally and get a better result from this than from the command line in your question, but my color vision sucks, so I can't guarantee that this is what you were after. =] Hope it gets you on the right track, anyway.
Related
I'm looking for an all-in-one solution for processing web images
Resizing
Cropping
Save as WEBP / JPEG / PNG
Drawing simple rectangles
Adding text
Reducing colors (quantization) for PNG
The only thing I'm not clear about is PNG quantization. Currently I'm using pngquant which works great, but I'd prefer to do everything in one place.
I see the SkiaSharp has SKImage.Encode() which takes a quality parameter. However there's no explanation as to what it actually is. Will this give me color quantization for PNG files? If not, is there something else in the library to do this?
I was writing a script to change my background on my Linux Machine to a random image from a set of images that contain only solid colors. What I would like to do is expand this script to also theme certain applications (mostly terminal ones) accordingly, at the very least to change the text color, possibly switch from dark to light background, etc. I was wondering what options I have to get the Hex Code for the color in the image. Is there something in bash I can do this with? Would I need to write a program in a more robust language and have the hex-code be the output? Is there a better way of doing this entirely? My searching thus far has been a bit inconclusive.
I would highly recommend to use ImageMagick for this task. The documentation mentions how to extract data from an image.
From "Extracting the average colour":
The average color of an image can be found very quickly by using "-scale" to reduce an image to a single pixel. Here for example is the average color of the built-in "rose:" image. I output the color using the FX Escape Format which
returns a color string that can be used directly IM without change.
user#laptop:~$ convert rose: -scale 1x1\! -format '%[pixel:s]\n' info:-
Will output: srgb(146,89,80)
In your case, replace rose: with an image file of yours, like foo.png.
If you want the output directly in hex notation, use this:
convert rose: -scale 1x1\! -format '%[pixel:s]\n' info:- | awk -F '[(,)]' '{printf("#%x%x%x\n",$2,$3,$4)}'
I'm trying to use optical character recognition (OCR) to read text printed on digital video (DV) tapes. I'm using cropped still frames from the video for the OCR process. The text is white, but there are color artifacts (maybe composite color artifacts) so that the white text has color bleeding onto it (see example below). The colors look to be in magenta-cyan-yellow colorspace, maybe?
OCR results would likely be improved if I could remove/filter those colors to leave only white on the text. Then I can create a binary black/white image. I can do this now, but I suspect results will improve if I can remove colors from the white text before OCR, and this will hopefully help separate the white text from the background image.
Are there any ways, using Imagemagick preferably, to filter out those colors from the white text? I'm not sure of the best way to approach this since there are multiple colors bleeding, and the background changes in each frame. Currently using Imagemagick version 6.9.2-3 Q16 x64 on Windows 7.
Sample full-frame image:
Sample of cropped region with text (note color-bleed and white text blending into background):
I would suggest leveraging ImageMagick's FX & Morphology Dilate to preprocess the image. But to be honest, it'll take a bit of trial & error to find the solution that would work for you. I would also recommend that whatever solution you develop allows graceful error handling (i.e. If attempted OCR process unsuccessful, emit warning, and progress video to next I-frame & repeat.)
Fx Preprocessing
The -fx operator will allow you to create user-defined mathematical expression. Some quick google search about chrome-keys, and other tolerance methods might be helpful. But for many OCR techniques, it's usually common to reduce the colors to a "uniformed" gray scale.
convert aaA7b.png -fx 'intensity' intensity.png
Morphology Preprocessing
Morphology allows common & custom kernels to alter surrounding pixels. As video scanlines + other artifacts are distorting the text, I would recommend exploring Dilate, but there are many other techniques listed in the Usage documents.
Diamond
convert aaA7b.png -fx 'intensity' \
-morphology Dilate Diamond:1 diamond.png
Square
convert aaA7b.png -fx 'intensity' \
-morphology Dilate Square:1 square.png
Plus
convert aaA7b.png -fx 'intensity' \
-morphology Dilate Plus:1 plus.png
Custom
And if you need something more exact, create your own kernel by supplying the following format size: row1 row2 ... rowN. In this example, I'm creating a 3x3 kernel with a single vertical line to offset the video scanlines.
convert aaA7b.png -fx 'intensity' \
-morphology Dilate \
'3x3: nan,1,nan nan,1,nan nan,1,nan' user_defined.png
But YMMV. Also take a look at Fred's TextCleaner script. The -deskew & -sharpen operators will help reduce the noise.
Sample of cropped region with text (note color-bleed and white text blending into background):
I think there's a saying "You can't make steak from a hamburger." or something like that. At some point the background will washout the text in the foreground, and it's time better spent to create a solution that acknowledges this.
I have image.png in truecolor,
palette.png (N colors, where N>256) or text file, where list RGB color palette.
How to get a picture with this palette?
If I use imagemagick:
convert image.png -remap palette.png remap_image.png
It does not work.
convert image.png -map palette.png remap_image.png
Gives a very bad quality. The image is very noisy. File size is bigger than before.
GIMP gives best quality:
Сonvert image to indexed color > use custom palette
But GIMP is GUI. I need to convert a lot images in the console without running the gimp and X.org.
Using a shared palette across multiple images requires a carefully crafted palette. If you don't take great care when using the palette of a single image across many images, the result will be poor.
This needn't be complicated though. If you have accesss to the GIMP (or other tool) which supports truecolor graphics, you can create a large image and fit all of the smaller images into it, then quantize the image to N colors, then use that palette as the source.
you should be able to closely mimic GIMP's behavior in the console using ImageMagick
Once you've got a truecolor image with all the colors you want to quantize,
# Create an 8-bit png from our source, with a 235-color palette as an example.
convert truecolor_source.png -colors 235 palette.png
# Create an 8-bit png from an arbitrary image and use the palette in palette.png
convert sample.png -map palette.png output.png
There are a number of options for down-sampling colors, like dithering. See the ImageMagickv6 example page for an excellent overview with example pictures and code.
Although I still don't exactly understand what you want to do, your currently most recent comment ("Yes, from RGB to palette will set independently. Need set correct quantity of colors"), it sounds like all you want to do is set a strict limit on the amount of colors of a bunch of images, but they don't need to use the same palette.
In that case, the solution is very simple:
convert sample.png -colors 135 output.png
Try playing with the quantization options if the result isn't to your satisfaction.
If the output image is too large for your liking, you can experiment with the -quality option.
If this still isn't satisfactory, please try to explain your goal in a more detailed manner.
Good luck!
cat photo.png | pngnq -s 1 > photoindexed.png
I tend to get good results with the "-remap" (single imge) or "+remap" (multiple images) functions in combination with "-colors". Read up on those functions here. Note that "with "-remap" you provide IM with the final set of colors you want to use for the image, whether you plan to dither those colors, or just replace the ones with their nearest neighbours.", meaning just remapping/replacing might not look good enough, as colors from the input image are simply replaced by those from the palette image. Some form of dithering will be necessary to distribute pixel color conversion errors throughout the output image, because not all colors in the palette match those of the input image.
I'd suggest you use the "-colors N" option for that. This will reduce your output image color count to a maximum of N. By default ImageMagick uses "-dither Riemersma" for this implicitly when you specify "-colors N". The are also other dithering options available.
I have a number of input images that contain multiple smaller images, all of them in a single row. All the contained images are the same size. So, for example, the image input.png may be 480x48 and contain 10 48x48 images, all in one row.
Using the imagemagick convert tool (or any other tool supplied with the defaul imagemagick suite), I want to write a bash script that takes an input image, the number of images to cut, and then cuts them all into individual images.
The user interaction i can do, but I've not been able to get convert to do the actual cutting. Can anyone suggest something? From reading the manual pages, i think this should work:
convert 'input.png[0x0+48+48]' output.png
but I get an error:
convert: no pixels defined in cache
tb_icons_l.png' #
magick/cache.c/OpenCache/3572.
convert: No IDATs written into file
1.png' #
coders/png.c/PNGErrorHandler/1391.
Any ideas?
I would do it like that:
convert input.png -crop 48x48 +repage +adjoin output_%02d.gif
Read more at Tile Cropping, in ImageMagick documentation.
I believe you've got the position and size swapped. Try:
convert 'input.png[48x48+0+0]' output.png
The third image would be:
convert 'input.png[48x48+96+0]' output.png
Or
convert 'input.png[48x48+0+96]' output.png