I’m trying to superimpose a batch of hundred black and white images so that they blend with 1% opacity and “darken only”. The multiplicity of. Imagemagick has a convert utility which can perform brightness and where is to darken by 30 and +10 is to increase the contrast by Images darken when getting converted with ImageMagick. When using ImageMagick to manipulate images, you might see that images get darker when beeing.

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How do I evaluate the result? The images are 8 bit grayscale, but each image is “thresholded” to black and white. Where do you put all the images?

However from IM v6. Under Construction Linear-Stretch In many ways ” -linear-stretch ” is very similar to the previous ” -contrast-stretch ” operator.

This was fixed as soon as I noted the problem and reported it. Questions and postings pertaining to the usage of ImageMagick imagrmagick of the interface.

If you want the old ” -normalize ” behaviour before IM v6. Test if inputdir exists Create outputdir Get list of images from inputdir Loop over each input image and create 3 output images in the outputdir. This colorspace is exacty the same as ‘ LCHuv ‘ but with the channel order reversed Hue stored in Red channel of the image, it was just teh way that colorspace is defined. So starting with your current large image, the following seems to work.

Using Overlay Compostion Tinting below will provide a more exact though very linear, rather than parabolic color tinting of mid-tone grays. Usage questions are like “How do Imabemagick use ImageMagick to create drop shadows?


Or the ‘I’ channel of HSI. The multiplicity of the black parts should become visible without being covered by the white parts.

It’s time to daarken the entire site. From that version onwards, as you can see above, it now uniformly tints all pixels including fully transparent pixels.

The ” -clut ” operator was added to IM v6. Thanks for your help. For example this is one DIY formula that imaegmagick can use They are the same colorspace, but ‘V’ is a confusing term, as a value normally means ‘a stored number’.

The best method of converting an image to gray-scale is to just ask IM to convert the image into a gray-scale Color Space representation for darekn image. This was changed because of a bug report by a user about the above situation. Normalise and other Histogram operators are really grayscale operators, caution is needed when using it with color images.

In ” -contrast-stretch “, counts start at zero with the lowest min and highest max populated bins in the image which may or may not be at bin 0 or bin in the histogram.

This however should not happen for real images, only images generated directly in the cylindrical space. Another new alternative is the Poly – Weighted Image Merging Operatorwhich will do the weighting and addition of the separated channel images in one operation, so avoiding ‘quantum rounding’ effects. That way, you do not have to hold all the images in memory at the same time.

As you can see gives a complete replacement of the color for a pure mid-gray, with no adjustment for either white or black.

[SOLVED] composite -blend 1% [and how to add “darken only”]? – ImageMagick

For more complex operations you can use the simpler Evaluate Operator” -evaluate “. The second question is, if IM can’t be made to do it: The above would suffer from ‘quantization’ effects for a ImageMagick compiled at a ‘Q8’ Quality Level. The latter would be the: Questions and postings pertaining to the usage of ImageMagick regardless of the interface.


Proceeding on the assumption that the above is correct, use the png16m device in Ghostscript darekn produce RGB PNG files directly, this reduces the scope of the problem: It will for example not work at all for a ‘black’ fill color. It will certainly give you a myriad of opportunities to alter the output.

The alpha composition method ‘ HardLight ‘ will produce the same results as ‘ Overlay ‘ but with the daarken and destination images swapped. For naming, just preserve the name for the bigger picture, while adding a 1 to the end of 1st thumbnail’s name and 2 to the darkened thumbnail’s.


However, with ” -linear-stretch “, if only one value, the black-point, is provided, then the white point will be the complement value. You’ll need to find out what Ghostscript command line IM is using and I can’t tell you how to do that. As such if you want five control points you need to include another ‘ e ‘ term to the function. The percentage argument is not a ‘blend percentage’ but really more a ‘brightness percentage’. The density was low so it is hard to see the true result.

Define a new outputdir. The batch of images are black and white and depict the shadow-shapes cast by a group of buildings: