CODEWITHSUNDEEP
c++linuximage-processingimagemagickimage-manipulation
Oded
Oded

Reputation: 664

Resizing animated GIF using GraphicsMagick

I have an animated gif image with transparent frames. I need to resize it.

Before resizing, I use the Magick::coalesceImages function, after I resize the image I use the Magick::writeImages function to collect all the gif frames back into one single image.

The problem is that the output resized image file size is bigger than the original one, because the original animated gif had transparent frames, and the new resized gif does not have any transparent frames.

I have read about frame optimization on www.imagemagick.org plus I can see on www.graphicsmagick.org the gifDisposeMethod function.

My question is, how can I cause the resized animated gif image to use transparency frames and avoid the increase on the image KBytes size?

Upvotes: 3

Views: 2773

Answers (1)

Oded
Oded

Reputation: 664

Well, I found the way to go:

When resizing an animated gif, using Magick::coalesceImages() is not the best way...

Instead I am rezising according to percentage sizing and not absolute sizing, while skipping the Magick::coalesceImages() call.

For example, lets say my original animated gif is 300x300 and I want to resize it to be 150x150, I'll do the following:

  • Read the image in a Magick::Blob
  • Calculate the percentage numbers (50%x50% in my demo case)
  • Resize each and every frame of the image according to the percentage calculations.

This way we are not increasing each frame size because we are not using the Magick::coalesceImages() function and we are resizing each frame according to its original size, so we don't have any problem with the transparency of the frame.

Upvotes: 3

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