im trying to resize image from 72x72 to 512x512 with following command
convert input.png -resize 512x512 output.png
but the output image (output.png) become blur
how to prevent resized images from becoming blurred
how to prevent resized images from becoming blurred
If you want a pixelated image of the original use -sample
# Create small image.
convert -size 72x72 plasma: 72x72.png
# Magnify the image with pixel subsampling.
convert 72x72.png -sample 512 512x512_sample.png
It's true that you can't restore missing data when upscaling images, but there's a lot of various algorithms to calculate what may be missing.
Try using the -filter option in addition to -resize, and checkout the wonderful usage examples here.
Probably the best you can do is use a sharper -filter such as catrom and then do post processing using -unsharp.
convert input.png -filter catrom -resize 512x512 -unsharp 0xSigma output.png
where sigma is the sharpening value, try sigma=1 or 2 (or as desired)
But it will not maintain the same quality as the input as others have mentioned above.
See -unsharp at http://www.imagemagick.org/script/command-line-options.php#unsharp
You can't. For an equal sharpness, you would need more data in the bigger image. Since you have only the data from a small image the result is blurred.
Look at it the other way, if what you asked was possible, instead of compressing the 512x512 image, we would first scale it down to 72x72, compress that (much smaller file) and sent it over with instructions to scale it up to 512x512.
Related
convert 0101.jp2 -threshold 50% -type bilevel -monochrome -compress LZW ../0101.tiff
The resulting image looks jagged when I use the above command to convert a colored scanned text page to a black/white image (must be one bit per pixel). I want to make it of a higher resolution to look smoother. How can I use convert to do so?
Note that SO automatically converts tif image to jpg format so the output image shown below is not the same as the output image. You will need to run the convert command to get the true output image in tif.
If instead of thresholding you apply a strong contrast the gray pixels on the edge remain in a range of grays and the output is not jagged.
convert Original.jpg -sigmoidal-contrast 30 Corrected.jpg
(there are several ways to increase contrast in Magick)
I would like to blur only a part of an image. The part to blur is always rectangular, so that I can easily use the following command:
magick source.jpg -region 1000x1000+0+500 -blur 0x20 result.jpg
This works, but is pretty slow for large images. Since I have to process thousands of files again and again, this will simply take too long.
Therefore, I decided to do the blurring by downscaling and upscaling the image back to the original size. However, since this will blur the full image, I have tried to accomplish the task using the following steps:
take the original image as background
create a copy of the original image
blur the copy using down-/upscaling
crop the desired region from the blurred copy
compose the original and the blurred&cropped copy
I am already pretty close (I hope), but when composing the two images, the cropped image will always be positioned in the top-left corner of the original image - instead of the original position from the source image. This is my current command:
magick source.jpg ( -clone 0 -resize 5% -resize 2000% -crop 1000x1000+0+1000 ) -composite result.jpg
I have read in the documentation that the original canvas size will be retained when using the -crop operation, and that this size and position will be used when using -composite. However, this doesn't seem to work in my case. Does anyone have an idea why?
I have tried to use -repage, -extent and other options to define the size and position of the cropped image, but to no avail so far.
I would try -flatten in your command as that is used for layers.
You can do it with a mask image (of any shape) in ImageMagick. Though I am not sure if that will be faster than your scaling method.
Input:
Mask:
(note: blurring occurs where mask is black)
magick lena.jpg -write-mask mask.png -blur 0x3 +write-mask lena_blurred.png
Result:
I've read the ImageMagick documentation here and here and been unable to achieve a couple of simple tasks. Would appreciate any simple pointers or direction, or even commands I can execute that will work on Linux.
I want to convert any image-type (JPG, GIF, PNG, TIFF) to save to a PNG, losslessly, and as compressed as possible without any loss of quality. Ideally in 96 DPI so they look good in Retina screens.
To then take the above generated PNG and also resize it in specific sizes, with height and width specified.
What am I missing with the convert command?
If you want to convert a TIF, GIF or JPEG to PNG, the command is:
convert image.tif result.png
or
convert image.jpg result.png
In answer to your questions...
Question 1
PNG is lossless by definition, so that is not an issue. To get better compression of a PNG, you generally need to reduce the colours, i.e.
convert image.jpg -colors 64 result.png # or try 255 which allows a palettised image
The dpi is pretty irrelevant until you print on paper. More pixels are needed if you want more quality on screen.
Question 2
If you want to resize an image without destroying its aspect ratio, use
convert image.jpg -resize 200x100 result.png # retain aspect ratio
If you don't care if that makes the image look stretched or distorted, and you want exactly 200x100, tell ImageMagick that you really mean it by shouting:
convert image.jpg -resize 200x100! result.png # ignore aspect ratio
I have a .eps file that I can look at in Photoshop, and it has a very high resolution, sharp edges, etc. at even larger than 1024x1024.
With ImageMagick I want to convert this .eps to a 1024x1024 .jpg with very high resolution.
However, with the following command, the image is very blurry:
convert -resize "1024x1024" -colorspace RGB -flatten test.eps test.jpg
What ImageMagick parameters do I have to use so that the resulting .jpg is 1024x1024 and a high quality, sharp image?
here's some XMP data we found, perhaps what is causing it to not be resized with -size:
For vector graphics, ImageMagick has both a render resolution and an output size that are independent of each other.
Try something like
convert -density 300 image.eps -resize 1024x1024 image.jpg
Which will render your eps at 300dpi. If 300 * width > 1024, then it will be sharp. If you render it too high though, you waste a lot of memory drawing a really high-res graphic only to down sample it again. I don't currently know of a good way to render it at the "right" resolution in one IM command.
The order of the arguments matters! The -density X argument needs to go before image.eps because you want to affect the resolution that the input file is rendered at.
This is not super obvious in the manpage for convert, but is hinted at:
SYNOPSIS
convert [input-option] input-file [output-option] output-file
Maybe you should try it with -quality 100 -size "1024x1024", because resize often gives results that are ugly to view.
I want to pixelate and/or blur an image.
I've found the command for the blurring:
$convert image.jpg -blur 18,5 newimage.jpg
to work but I cannot blur the image any more.
And how do I pixelate the image? I couldn't find a sound example around the net.
Thx
To get a proper square pixellation, try:
convert -scale 10% -scale 1000% original.jpg pixelated.jpg
This worked nicely for me, gives a sort of cross between pixelating and blurring:
convert -resize 10% image.jpg newimage.jpg
convert -resize 1000% newimage.jpg newimage.jpg
You can be sure that the data cannot be retrieved, should that be important to you.
Changing the %ages will change the amount of pixelation/blur
I don't know anything about ImageMagick, but you can try resizing the image using bicubic to a much smaller dimension, then resizing the image back to a bigger one.
The trick works using .net's System.Drawing object.