I have an animated GIF which is color, I would like to make it grayscale. How can I do this with ImageMagick? I've tried using this:
convert image.gif -fx "(r+g+b)/3" imageGS.gif
But this leaves me with a grayscale image that is just the first frame of the animation.
How do I tell ImageMagick to affect all the frames of the animation?
Use the modulate command instead and set the saturation to 0:
convert image.gif -modulate 100,0,100 imageGS.gif
I tested this with my own animated gif and it worked.
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'm uploading base64 encoded image to a RoR application. When I receive the image, it has a rgb color scheme (correct), when I write the image on file to be uploaded with paperclip gem, the image color scheme change from rgb to grayscale.
Here is the code:
source = src.gsub(/^data:image\/(png|jpg|jpeg);base64,/,"")
blob = Base64.decode64(source)
img = Magick::Image.from_blob(blob).first
img.colorspace = Magick::SRGBColorspace
img.add_profile "#{Rails.root.to_s}/lib/color_profiles/RGB.icc"
img.write(url = "#{Rails.root.to_s}/tmp/#{self.id}_logo.png")
image = File.open(url)
the img is correctly a RGB image, if I check the resulted created file:
identify -format "%[colorspace]" #{url}
the color scheme is Gray.
Additional info:
The uploaded image is all black with white text, if I upload same image with red background, the final image is correctly an RGB image.
There seems to be a bug in ImageMagick 6.9.9.27 and 7.0.7.15 when reporting the conversion of a grayscale image to RGB PNG. Identify -verbose is reporting grayscale but the string format %[colorspace] is properly reporting sRGB as are the PNG tags. I have reported this bug. For example:
convert logo: -colorspace gray logo.jpg
convert logo.jpg PNG24:logo.png
convert logo.png -format "%[colorspace]" info:
sRGB
identify -verbose logo.png
...
Colorspace: Gray
...
png:IHDR.color-type-orig: 2
png:IHDR.color_type: 2 (Truecolor)
I do not understand. Is your image a color image or a grayscale only image?
IM 6.7.7.10 was during a time that ImageMagick was changing from non-linear gray to linear gray and back again. And also had RGB and sRGB swapped. So you may have a version where gray was linear (darker than non-linear gray) or where RGB and sRGB were swapped. You can convert back to non-linear using one of the following (I do not recall which to use at this time). The other will convert from linear to non-linear. If I assume your input image was grayscale and not color, then try one of these:
convert input -colorspace RGB -colorspace gray result
or
convert input -colorspace sRGB -colorspace gray result
If it is not grayscale, but color only, then leave off the -colorspace gray in these commands.
I would urge you to upgrade if you can. You are well over 200 versions old.
P.S. It is also possible your profile is causing a problem. I don't know what the RGB.icc profile is. Is that an Adobe RGB profile or an sRGB profile.
Can you reproduce your problem using Command Line ImageMagick? If so, post the command line you used. Sorry I do not know Ruby or RMagick.
P.S. 2 Apart from the lighter/darker issue, if you are trying to convert a grayscale image to color, then you will need to specify the output as PNG24:name.png. That is the only way to force a grayscale image to report colorspace=RGB without inserting color pixels.
Using shell commands, I can perform the following on a PNG file that has transparency:
convert image.png -background Black -flatten image.png
And the resulting image now has a black background. How do I do this with the Magick++ API? I have an Image object that I'm using already for some other manipulation:
Image img(filename);
img.resize(Magick::Geometry("x48"));
img.unsharpmask(5.0, 0.5, 50.0, 50.0);
img.gamma(0.5);
...
Before I do the resizing, I need to take care of the image transparency and make it black instead.
Thanks.
The -flatten option can be found in STL.h and is called flattenImages. This method requires a container of images. Below is an example of how you can use the method.
Image img(filename);
Geometry size(img.columns(), img.rows());
Color color(0,0,0);
Image black(size, color);
std::list<Image> images;
images.push_back(black);
images.push_back(img);
Image flattenedImage;
flattenImages(&flattenedImage, images.begin(), images.end());
flattenedImage.resize(Geometry("x48"));
I have an image in .jpg format with white background color. I want to remove the white background color to transparent in Imagemagick. I tried many ways but still the white background can not be removed. Can some one help me to solve this.
You cannot have transparent background colors in your JPEGs. The JPEG file format doesn't support transparency.
If you need transparent background, you need to convert the JPEG to
either PNG (high quality, filesize possibly larger than JPEG)
or GIF (in case you can tolerate low quality and a range of maximally 255 colors).
Example command:
convert your.jpg -transparent white your.png
First, you need to convert the image format from .jpg to .png format, because JPEG does not support transparency. Then use this command:
convert image1.png -fuzz 20% -transparent white result.png
The -fuzz option allows the specified percentage deviation from the pure white colour to be converted to transparent as well. This is useful, for example, when your image contains noise or subtle gradients.
I just found a very neat thing!
magicwand 1,1 -t 20 -f image -r outside -m overlay -o 0 image.jpg imgOutput.png
It is a Fred Weinhaus bash script that can be downloaded from here (for non commercial use only). Also there has about 250 scripts!! and this one is amazing! it did exactly the trick, to remove all background while keeping the inner image dots untouched!
At his page, there are several images as examples so you pick what you need to put on the command line!
The initial position 1,1 is a general guesser saying all the contour is background.
Pay attention that the output must be ".png"
This is my solution without magicwand (replace magick by convert for im < 7.0):
magick img.png -fuzz 20% -fill none -draw "alpha 1x1 floodfill" result.png
Get the background automatically and remove it :
bg=$(convert input.png -format "%[pixel:p{0,0}]" info:)
convert input.png -fuzz 20% -transparent "$bg" output.png
I have some PNG files I wish to convert to 256 colors (i.e. GIF-like). Each image has transparency, but when I try to convert I always end up with a black background on the resulting image.
Here is my current command:
convert file.png -colors 255 file256.png
I'm using 255 colors because I read that you need one color for the alpha channel (though I don't think that should apply to PNGs). I've tried many other options such as -background none, -channel RGBA and -matte but nothing is working at all.
Interestingly, this command did work when converting to grayscale:
convert file.png -channel RGBA -matte -colorspace gray file256.png
It kept the transparent background. But replacing -colorspace gray with -colors 256 doesn't work.
The reason to use 255 instead of 256 colors is that one color needs to be reserved for "binary" / "boolean" transparency, i.e. all pixels of that color are interpreted as completely transparent. There (usually) is no such thing like an alpha channel with 256-color / palette-based images. For reference, you may want to read the ImageMagick usage sections about Color Quantization and Transparency and GIF Boolean Transparency. That said, this should convert your 32-bit true-color PNG with alpha channel to an 8-bit PNG with palette where all pixels that are fully transparent in the input image are also fully transparent in the output image:
convert file.png png8:file256.png
The png8 instructs ImageMagick to write a GIF-like "8-bit indexed with optional binary transparency" PNG and implies to use 255 "real" colors.
Have you tried -colorspace transparent to preserve the Alpha channel?