Legacy ImageMagick Discussions Archive

The C channel of LCHab is improperly scaled in memory, and so clips. The clipping is bad enough that even the sRGB colorspace does not quite fit in the current implementation of LCHab. It easily could be made to include all of Lab. I believe the valid channel ranges are: L 0 - 100 (same value as in ...

This output appears incorrect: > convert -size 1x1 xc:#0FF -colorspace Lab txt:- # ImageMagick pixel enumeration: 1,1,65535,cielab 0,0: (91.1147%,-18.8556%,-5.54665%) #E940 00000000 cielab(91.1147%,-18.8556%,-5.54665%) In memory, IM stores a & b offset by #8000 to handle negative values. This is...

Are the cylindrical color spaces (HSV/HSB, HSL, HSI, HWB, HCL) inherently sRGB-based? I have always thought of them as mathematical constructs that could be applied to any RGB colorspace, but I discovered that ImageMagick implicitly expands convert hald:10 -set colorspace RGB -colorspace HSL ... to ...

Agreed, it appears that -append carries out implicit colorspace conversions. I believe that it automatically converts all images to sRGB before appending the images together, then converts the result to the colorspace of the first image. This would explain the above rounding error, and the lost proc...

Create a hald image using IM. Append it to your image and save in a lossless format. Make the adjustments in whatever program you like (including IM). Crop out the now adjusted hald image. Use IM and the adjusted hald color look-up table to apply the adjustment in batch to all your images.

Some of your shrinkage could have been the loss of metadata. Rather than judging by file size, you can use IM's compare to quantify the loss.

snibgo is right that this can be quite complex, so creating your own solution will only get you so close. Adjustments may be easier in a cylindrical color space, i.e. one with hue. If you can achieve the adjustments you want using GIMP, Photoshop, etc, you can use snibgo's hald-clut suggestion to ca...

With ImageMagick, as with most image tools, simply opening and resaving a jpeg results in recompression and a tiny, often imperceptible, loss of quality. If you must use jpeg and really need zero loss, jpegtran is a specialized tool that may help. Specifically, look at crop 'n' drop. jpegtran can av...

Have you looked at -extent? It doesn't require a background image and should keep your metadata.
http://www.imagemagick.org/script/comma ... php#extent
http://www.imagemagick.org/Usage/crop/#extent

snibgo wrote:I would put this down to a rounding difference.

Agreed that it is small, but are pixels being rounded by -append or -set colorspace?

ImageMagick 6.8.8-1 Q16 x64 2013-12-25 on Windows 7

Does -set colorspace modify pixel values, or only change the colorspace setting? convert -size 500x1 gradient:#000-#F00 gradient:#FF0-#000 -set colorspace RGB -resize 450x1 -set colorspace sRGB -append y.png convert -size 500x1 gradient:#000-#F00 gradient:#FF0-#000 -set colorspace RGB -resize 450x1 ...

Thanks to all for the input! In Lightroom any modifications are added to an XMP file and only applied in lightroom. The Sony version of Lightroom, Image Data Converter\Image Data Converter Ver. 4.0, saves modifications to the raw file itself. That is why I was hoping to choose either the raw or corr...

You applied a curve to a Hald using IM or something else? Is the new file also 8-bit png? Have you tried increasing the compression?

It is not surprising that the new file is larger, but that does seem huge.

Yes, like that! I don't know if WIC is widely supported, but a generic connector like WIC is definitely better to support.

Using ExifTool, I learned that my Sony file contains both a 160x120 thumbnail and a 1616x1080 preview jpeg. Maybe Windows Explorer simply uses the preview image?

I wouldn't expect IM developers to care specifically about Sony's driver. I just didn't know if there was a Microsoft COM framework or something to provide a common interface for images, like DirectShow is for audio and video codecs. It's all new to me, and probably over my head.