Quicker ways to combine two images in Magick.net

[herbertgzb]

The task I am going through is rather straightforward -- I need to read either a GROUP IV tiff image or a jpeg image. I then need to either cut a slice in the that image or to annotate it. Either way -- using magick.net I would think the first task is to cut the image into two pieces (top and bottom) and cut out the middle part, and combine them. The second task would be to create a canvas and write on that canvas with the original image and the annotation.

A sample code for the first task would be like this (after I have

'read in image
Dim image_top As New MagickImage(inputpath.ToString)
 Dim image_bottom As New MagickImage(inputpath.ToString)

'crop top slice and bottom slice with specific heights
image_top.Crop(image_top.Width, image_top.Height - CInt(centerslice_height.Text) - CInt(bottomslice_height.Text), Gravity.North)
image_bottom.Crop(image_bottom.Width, CInt(bottomslice_height.Text), Gravity.South)

'Combine top and bottom slices
Dim output As New MagickImageCollection
output.Add(image_top)
output.Add(image_bottom)
Dim IMAGE As New MagickImage(output.AppendVertically)
IMAGE.Format = MagickFormat.Tiff
IMAGE.Settings.Compression = 8
IMAGE.Write(outputpath)

Up to the "IMAGE.Write(outputpath)" line, everything took around 80ms. The final line takes around 1500ms/1.5s either writing on network share or locally.

If the task is simpler/not involving combining the two images together, aka, like below

Dim image_top As New MagickImage(inputpath.ToString)
image_top.Crop(image_top.Width, image_top.Height - CInt(centerslice_height.Text) - CInt(bottomslice_height.Text), Gravity.North)
image_top.Write(outputpath)

The above code takes around 80ms to finish. Note that -- the image_top contains most of the whole image (image top is around 3100 pixels while image_bottom is around 100 pixels). So I don't think size itself is the problem here.

I have also tried the composite method (I believe for annotation I'll use the same method)

'read in image
Dim image_top As New MagickImage(inputpath.ToString)
Dim image_bottom As New MagickImage(inputpath.ToString)

'crop top slice and bottom slice with specific heights
image_top.Crop(image_top.Width, image_top.Height - CInt(centerslice_height.Text) - CInt(bottomslice_height.Text), Gravity.North)
image_bottom.Crop(image_bottom.Width, CInt(bottomslice_height.Text), Gravity.South)

'use a canvas to write top/bottom slices
 Dim settings As New MagickReadSettings()
settings.Width = image_top.Width
settings.Height = image_top.Height + image_bottom.Height
settings.Compression = 8
Dim IMAGE = New MagickImage(outputpath, settings)
IMAGE.Format = MagickFormat.Tiff
IMAGE.Composite(image_top, 0, 0)
IMAGE.Composite(image_bottom, image_top.Height, 0)
IMAGE.Write(outputpath)

And again -- the last step take 1.5s vs everything before the IMAGE.Write(outputpath) line taking less than 80ms.

Wonder if I can do anything to make the whole process quicker?

Thanks in advance!

[dlemstra]

Without your images I cannot really give you a good answer. I suspect that the compression is what is making it take the 1.5s on your machine.

[herbertgzb]

Are you using the 64-bit build? Maybe you are running into 32-bit memory limits?

For this part I might need to test on that. I am using the 64-bit build.

[dlemstra]

It turns out that you helped me find an optimization inside Magick.NET. I would advise you to use image.DetermineColorType(); after I have published a new version of ImageMagick. This will change the type of this image to Bilevel instead of doing an expensive Quantize operation inside the TIFF encoder.

And I will also try to figure out why the type of this image was changed when doing the Crop and AppendVertically operation. It could remain Bilevel instead. But I am not sure if I can make this change,

[herbertgzb]

It turns out that you helped me find an optimization inside Magick.NET. I would advise you to use image.DetermineColorType(); after I have published a new version of ImageMagick. This will change the type of this image to Bilevel instead of doing an expensive Quantize operation inside the TIFF encoder.

And I will also try to figure out why the type of this image was changed when doing the Crop and AppendVertically operation. It could remain Bilevel instead. But I am not sure if I can make this change,

Great to know and thanks!
To clarify -- I should do this before I do the crop, right? And also before the append vertically? But the appendvertically is done the same time as I define the object?

[dlemstra]

Sorry for the late response @herbertgzb. The DetermineColorType operation should indeed be the first one. I also added another optimization in the latest version of Magick.NET that will keep the image as Bilevel in the call to AppendVertically. That should improve the performance even more.

[herbertgzb]

Sorry for the late response @herbertgzb. The DetermineColorType operation should indeed be the first one. I also added another optimization in the latest version of Magick.NET that will keep the image as Bilevel in the call to AppendVertically. That should improve the performance even more.

Thanks a lot! I'll definitely check out the latest release!!