I need to generate low resolution black and white images of texts in ImageMagick. These images will be plotted in a small LED matrix. The text need to have 7 pixels of height.
For now, I'm using:
convert -negate -threshold 15% -font Courier -size 80x11 caption:'hello' out.bmp
Output image:
Even with the height being more than I need, due to low resolution and anti-aliasing correction, the letters are not pretty and symmetric. Has anyone did this and can help me out?
Version: ImageMagick 6.8.9-9 Q16 x86_64
The solution I found was to use an TrueType font. Just got a free font from the internet and used it in the size it was built for.
P.S.: Switched for OpenCV as well. My Python app generates images dynamically. The cost for invoking ImageMagick several times(could get close to hundred) per minute is too high.
Posting a snippet, hope it helps.
import cv2 as cv
from PIL import ImageFont, ImageDraw, Image
# Creates a black image with 80x10 size
img = Image.new('RGBA', (80, 10), (0,0,0,0))
draw = ImageDraw.Draw(img)
# Load TrueType font of height size 8
font = ImageFont.truetype("font.ttf", 8)
# Draw text using the loaded font
draw.text((0, 0), "Hello World!", font=font)
img.save("out.bmp")
Output Image:
I would be inclined to output the letters larger than required, then to trim any extraneous spare space so as to make the most of the available resolution, then resize down to your specific needs:
convert -size 320x32 -font Courier label:'hello' -trim +repage -resize 80x8 +write out.gif
Mark, I think he wants a binary result. But you have an excellent idea.
Let's take Mark's result, threshold and then scaling down to 8 pixels tall. This ImageMagick command seems to work better than my earlier post.
Mark's Output:
convert wcwuj.gif -threshold 60% +write thresh.gif -scale x8 result.gif
Threshold Result:
Scaled Result:
Perhaps making Mark's image much larger and choosing a better threshold will produce a better result.
You have not told us what version of ImageMagick nor platform and you do not show your result for us to see what might be wrong. Also your ImageMagick syntax is not proper, though ImageMagick 6 is rather forgiving.
This is what I get using ImageMagick 6.9.10.8 Q16 Mac OSX Sierra. The first output is 8 pixels tall and the second output is scaled by 1000% (10x).
This forum does not seem to convert bmp to a usable format for display, so I am using GIF in place of BMP. But my results look the same whether BMP or GIF
convert -size x8 -font Courier label:'hello' -negate -threshold 20% +write out.gif -scale 1000% out2.gif
I have tried changing threshold, but much larger or smaller values make it worse. A range from about 10-30% produces the same results.
I have also tried using -monochrome in place of -threshold and get the following:
convert -size x8 -font Courier label:'hello' -negate -monochrome +write out3.gif -scale 1000% out4.gif
You might try a dot-matrix type font. See https://www.1001fonts.com/digital+dot-matrix-fonts.html?page=1&items=10. I have not tried any of them.
You could try some of the old X11 fonts. These were hand-drawn rather than being rendered from a set of curves, so they look good at very small sizes.
For example, if I run xfontsel I get things like this (enlarged for clarity):
Take a look in /usr/share/fonts/X11/misc.
Related
I've got an 540x540 image of 54x54 color squares (same sizes).
When I resize it to 54x54px it looks horrible (blurred), shouldn't a resize like this be perfectly done with imagemagick?
is I possible to get it perfect?
I've tested convert source.png -resize destination.png and -adaptive-resize but the result is the same..
I see what your confusion is now... the problem is not that the process is lossy, rather it is because the -resize is doing more sophisticated processing than you want in order to make an attractive job that you would want for, say, photographs. You want a very simple point sampling process which will produce simple blocks of pure, uncombined colour.
I'll make a start image:
magick -size 10x10 xc:red +noise random -scale 540x540 start.png
And scale it down, by taking a point sample in each block:
magick start.png -sample 10x10 small.png
And back up:
magick result.png -scale 540x540 reincarnated.png
I am converting many 3D textures with imagemagick for a video game. My source files are png, my target files are png, too. But I notice that whenever the alpha channel drops to 0.0 my color information are gone (and I need them). I just want to scale all channels as they are. I guess there is a small switch that fixes that problem, but the deadline is near and I cannot find anything about that.
Simple command to reproduce this:
convert source-with-alpha.png -scale 2014 target.png (I also tried -resize and it also didn't work).
Doing just convert source-with-alpha.png target.png works fine though (but has no scaledown).
Thank you for your help.
I guess ImageMagick is trying to optimise something but not sure what/why. Maybe the idea is that if something is transparent you can't see it, so we might as well make it black so it compresses well.
Anyway, try separating the channels so they are all just treated as independent channels, then resizing and recombining:
convert input.png -channel RGBA -separate -resize XxY -combine result.png
I am not sure I understand your problem. I have no issue resizing a transparent PNG image with ImageMagick 6.9.10.28 Q16 Mac OSX with libpng 1.6.36. Perhaps you need to upgrade one or both.
Image:
Make white into transparent:
convert logo.png -transparent white logot.png
Resize it:
convert logot.png -resize 25% logot_small.png
I tried Mark Setchell answer with two different versions of Windows imagemagick but I still have this issue.
RGB becomes 0 if alpha is 0 when resizing.
A workaround was to add alpha a little bit so it becomes non-zero:
magic.exe input.tga -channel a -evaluate add 0.2% -channel RGBA -separate -filter Quadratic -resize -resize XxY! -combine result.tga
or also (same result)
magick.exe ( input.tga -alpha off -filter Quadratic -resize XxY! ) ( input.tga -filter Quadratic -resize XxY! -alpha extract -evaluate add 0.2% ) -compose Copy_Alpha -composite result.tga
("-filter Quadratic" is optional)
Post one of your tga files so we can test with it. What is your ImageMagick version? There should be no need for any switch. This works fine for me on IM 6.9.10.65 Q16 Mac OSX.
Make a transparent TGA:
convert logo: -transparent white logo.tga
transparent tga image
Resize by 50%
convert logo.tga -resize 50% logo2.tga
resized transparent tga image
How how would i generate an image of certain resolution containing black and white noise. I want to generate a number of images with each images noise being different. Prefer if done in console of either linux or windows but coding is ok if really have to.
Cheers
Like this with ImageMagick which is installed on most Linux distros and is available for macOS and Windows:
convert -size 512x512 xc:gray +noise random -colorspace gray noise.jpg
Replace convert with magick if using v7+ of ImageMagick.
If you mean pure black and white without shades of grey, and maybe would like a different size and a PNG format, use:
convert -size 600x400 xc:gray +noise random -colorspace gray -threshold 50% noise.png
If you want a different distribution of noise (gaussian, poisson, binomial) or to attenuate the noise, have a look at my other answer here.
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
I have image like this from my windstation
I have tried get thoose lines recognized, but lost becuase all filters not recognize lines.
Any ideas what i have use to get it black&white with at least some needed lines?
Typical detection result is something like this:
I need detect edges of digit, which seams not recognized with almost any settings.
This doesn't provide you with a complete guide as to how to solve your image processing question with opencv but it contains some hints and observations that may help you get there. My weapon of choice is ImageMagick, which is installed on most Linux distros and is available for OS X and Windows.
Firstly, I note you have date and time across the top and you haven't cropped correctly at the lower right hand side - these extraneous pixels will affect contrast stretches, so I crop them off.
Secondly, I separate your image in 3 channels - R, G and B and look at them all. The R and B channels are very noisy, so I would probably go with the Green channel. Alternatively, the Lightness channel is pretty reasonable if you go to HSL mode and discard the Hue and Saturation.
convert display.jpg -separate channel.jpg
Red
Green
Blue
Now make a histogram to look at the tonal distribution:
convert display.jpg -crop 500x300+0+80 -colorspace hsl -separate -delete 0,1 -format %c histogram:png:ahistogram.png
Now I can see all your data are down the dark, left-hand end of the histogram, so I do a contrast stretch and a median filter to remove the noise
convert display.jpg -crop 500x300+0+80 -colorspace hsl -separate -delete 0,1 -median 9x9 -normalize -level 0%,40% z.jpg
And a final threshold to get black and white...
convert display.jpg -crop 500x300+0+80 -colorspace hsl -separate -delete 0,1 -median 9x9 -normalize -level 0%,40% -threshold 60% z.jpg
Of course, you can diddle around with the numbers and levels, but there may be a couple of ideas in there that you can develop... in OpenCV or ImageMagick.