Using ImageMagick's convert utility to convert some scanned jpg files to pbm files.
However, even if the option -quality 100 is used, the pbm's resolution still looks worse than the original scanned jpg file.
Worse, the scanned jpg file is a colored one, while the converted pbm is black and white.
Info of original jpg:
image size: 2256 × 1568 pixels
dpi: 300 pixels/inch
color model: RGB
info of the converted pbm:
image size: 2256 × 1568 pixels
dpi: 72 pixels/inch
color model: Gray
Currently, here is what I did to convert the format:
qiang#bonjour:~/scan$ convert scan000.jpg scan000.pbm
Am I missing any option to use with convert? As I mentioned earlier, -quality 100 had been tried, but to no avail.
Using ImageMagick, I think you want to output to PPM not PBM. Try
convert image.jpg image.ppm
or try the ascii version by using
convert image.jpg -compress none image.ppm
PBM is binary (black/white) and PGM is grayscale. If you want to keep color, then you need to use PPM.
Unfortunately, I believe that ImageMagick can only read DJVU format images. So you cannot write to it directly from ImageMagick.
Related
I am converting a pdf to .tiff file using ImageMagick and calling it from python using subprocess,run() but, I want the output file size to be limited to a maximum value say 40MB. -define extent max_value is not working for tiff like it works for jpeg images.
This is my code:
subprocess.run('magick convert -density 150 example.pdf -trim -thumbnail 500 result%04d.tif')
I have tried adding the option -depth 12 to the string
convert transparentPNG.png -resize 500x400 -background white -flatten -depth 12 png_small.jpg
The input file is a transparent png to which I'm adding a background and then changing the depth. But the depth remains the same as 8bits. I verified the same using the -verbose.
I'm not sure what could I be doing wrong here. I'm referring to the site link
The transparent input png file used for my test can be found here
Let me know if you have any questions on the tests i did. Hoping to get some tips.
A JPG can only be 8-bit, so your internal 12-bit image is converted back to 8-bit when you save the result.
I've tried using image magic but it converts the image into a compressed format and most of the online conversion tools are also doing the same thing.
Is there some way i could achieve this in image magic or anywhere else?
Use the ImageMagick "-compress none" option to prevent compression, and use "-define bmp:format=bmp4" to force BMP4.0:
convert in.jpg -define bmp:format=bmp4 -compress none out.bmp
You can omit defining the bmp4 format because that's the currently the default BMP output format for ImageMagick anyhow.
Add "-alpha on" if you need RGBA instead of RGB pixels.
See the ImageMagick documentation for the -compress and -define options.
My goal is to create a Tiff image that natively holds uncompressed (or with lossless compression) YCbCr data inside (since the original image is YUV420 and IMO it would be a poor choice to upsample and convert to RGB).
I’m able to create (using imagemagick for instance) a valid YCbCr Tiff with a JPEG compressed data. When I try uncompressed / deflate / lzw I get a broken image (neither windows image viewer nor photoshop can open it). On page 94 of the TIFF 6.0 spec (under “Minimum Requirements for YCbCr Images”):
Compression = none (1), LZW (5) or JPEG (6). SHORT.
What’s wrong? Is there a Tiff extension which says that YCbCr color space is supported only when using jpeg compression?
Thanks,
Mark.
Command that works:
convert infileRGB.tif -colorspace ycbcr -compress jpeg outfileYCbCr.tif
Commands that don't work (broken tiff):
convert infileRGB.tif -colorspace ycbcr -compress none outfileYCbCr.tif
convert infileRGB.tif -colorspace ycbcr -compress lzw outfileYCbCr.tif
I created an 8-bit .tiff image ("test.tiff") containing a grid of 30 different color patches in the RGB color space using ImageMagick -convert.
When I convert this image into a jpeg (which is what I need) using:
convert -quality 100 -colorspace RGB -depth 8 test.tiff test.jpg
The identify -verbose command reveals that the resulting jpeg has several additional colors in the color table, each only taking up a few (1-4) pixels and residing very near the desired colors in RGB space. My assumption is that some kind of border bleeding is happening; maybe due to compression?
I don't understand why this border bleeding has occurred, especially given that it does not occur when I convert the tiff image to either a bmp or pcx image.
Thank you
By definition, JPEG is a lossy compression. The effects your experiencing are expected with the JPEG format. Setting the -quality of 100 will not have a 1-to-1 image result as tiff.
See additional answers:
Should I use JPG or TIFF for high-quality prints?
[...] because every time [JPEG] would save it it would generate some changes.
Is Jpeg lossless when quality is set to 100?
At [quality] 100, you just get the LEAST loss possible.
I don't know how you created your 30 colour swatch, or how your histogram looks, but you might try adding -dither None and -colors 30 options to your convert commands:
convert test.tiff -dither None -colors 30 ...