I'm using the following command to resize all the images in a folder:
convert folder\*.png" -format jpg -resize 1573 -quality 70 -strip -density 72 -interlace Plane -set filename:fname %t-1 +adjoin "C:\Users\%USERNAME%\Desktop\New folder\%[filename:fname].jpg"
It works, but instead of resizing to 1,573 pixels, I'd like to resize to 8.5 inches in width and 11 inches in height. How can I do that using ImageMagick Convert?
The "print size" of an image is the combination of its size in pixels and it print resolution, the matter being just metadata:
print size (inches) = size in pixels ÷ print resolution (in PPI)
So to change your image to 8.5×11 inches you can just change the resolution:
Necessary resolution = 1513 pixels ÷ 11 inches = 138PPI
The usual tool to edit metadata is ExifTool:
exiftool -xresolution=138 -yresolution=138 -v2 your_image.jpg
This of course assumes that your image is already in the 11 ÷ 8.5 aspect ratio. Otherwise you compute different X and Y print resolutions or first crop the image to achieve the proper aspect ratio.
Also, watch out for low resolution values. If you have text or sharp lines in the image (logo, CGI) 150PPI is on the low side...
I am trying to reduce image width and height from 600*400 to 120*120 using following comment in imagemagick
convert 'old.png' -resize 120x120 -quality 100 'new.png'
After reducing size image looks too blur.
Is there any way to do this using imagemagick?
You could try sharpening your image with -unsharp 1.5x1+0.7+0.02
I have huge texture Nx1024 pixels. I split it into several 1024x1024 textures with the following command with Imagemagick:
magick image.png -quality 100 -background none -resize x1024 -crop 1024x1024 -extent 1024x1024 output%02d.png
How can I add 2 pixels overlap on left and right sides of output images or duplicate pixels with imagemagick?
PS:
I found the following case (-crop 3x1+2#) crop with equal size but it doesn't suit because I have an unknown width of the input image (it could be multiple of N for 1024)
If on Unix-based OS, then you could try my script, overlapcrop at http://www.fmwconcepts.com/imagemagick/index.php
I am using ImageMagick to reduce the image resolution, height and width.
I have noticed a few things. When I am changing resolution at "Image Size" through Photoshop (version 7) from 300dpi to 150dpi image height and width automatically change.
With ImageMagick however I am not getting such variations. For example, if image contains 878 width and 179 height at 300dpi, when changing it to 150 dpi, automatically the image width changing to 439 and height 89 respectively.
Can any one support me how to obtain such changes through ImageMagick.
The dpi setting is not really relevant in most imaging applications/areas, until the point at which you want to print an image.
Do you really need to set it? I mean, if you want to half the size of an image, just use ImageMagick and do:
convert input.jpg -resize 50x50% output.jpg
and ignore the dpi.
To resize the image keeping the rendered size the same, you can use the -resample
option, like so:
$ convert original.jpg -resample 150x150 new.jpg
Using your example, if the original is an 878x179 image at 300DPI,
the result is an 439x90 image at 150DPI:
$ file original.jpg
original.jpg: JPEG image data, JFIF standard 1.01, aspect ratio, density 300x300,
segment length 16, baseline, precision 8, 878x179, frames 3
$ file new.jpg
new.jpg: JPEG image data, JFIF standard 1.01, aspect ratio, density 150x150,
segment length 16, baseline, precision 8, 439x90, frames 3
You can alternatively use the
-density
option along with the
-resize
option to achieve the same effect:
$ convert original.jpg -density 150x150 -resize 50%x50% new.jpg
In summary:
-density
just sets the DPI metadata without changing the underlying image;
-resize
changes the image size without changing the DPI;
-resample
changes the DPI and resizes the image accordingly.
Uses
The DPI metadata is relevant when you need to print an image or convert it to a PDF.
Now you can convert both images to PDF and get files with essentially the same page size:
$ convert original.jpg original.pdf
$ convert new.jpg new.pdf
$ pdfinfo original.pdf | grep -a "Page size:"
Page size: 210.72 x 42.96 pts
$ pdfinfo new.pdf | grep -a "Page size:"
Page size: 210.72 x 43.2 pts
I converted a 2.9M jpg to a 20x20 using 8 as the quality. but that file's size is still 48k.
here is my command
convert 238832c58dc3bc0b_29M.jpg -quality 8 -resize '20x20>' +repage 238832c58dc3bc0b_20x20.jpg
and after conveted, 238832c58dc3bc0b_20x20.jpg is 48k. I tried smalled size and quality, still 48k. it shouldn't be so big. it should be less than 10k. anybody know how to enhance it? thanks
Use -thumbnail instead of -resize or add -strip to your command.
Thumbnail removes the EXIF information apart from the color profile and strip removes the color profile as well.