Wrong size of final image after resize about resize HOT 5 CLOSED

Click "Network" to see my suggested fix for this ("improve-canvas-size") and other issues.

from resize.

Hi Jason,

thank you for your reply. I switched to your branch to give it a try and I have to say you did amazing work, results are perfect. I can see only one problem. It seems that after resize there appears some kind of border when I use other filter than NearestNeighbor and save as JPG, why is it so and is it intent?

Saved as JPG:

Bicubic

Bilinear

Lanczos2

Lanczos3

NearestNeighbor

MitchellNetravali

When I save result image as PNG the resulting images are with some black parts:

Bicubic

Bilinear

Lanczos2

Lanczos3

MitchellNetravali

NearestNeighbor

from resize.

This isn't the appropriate place to suggest using fpresize instead (disclosure: I am the author), but GitHub doesn't have private messaging, and you have no contact info.

I don't know what the problem is with the PNG images. Looks like some sort of numeric overflow/underflow. I'll look into it when I get a chance.

The border around the JPEG images is there because nfnt/resize uses transparent virtual pixels. That's useful sometimes, but it's not good if you're going to write the image to a file format that does not support transparency.

Assuming the original image did not have any transparency, then stripping the alpha channel before writing the JPEG file is probably the best thing to do (i.e. set each pixel to have maximum opacity).

from resize.

The PNG corruption is caused by invalid combinations of color and transparency values. I fixed it in my copy of the project.

from resize.

Issue is fixed. I pulled in the fixes from Jason, thanks you!
FYI, the "black parts" issue was caused by the way Go's image packages handles accessing value outside the image boundaries. It returns constant zeros, also on the alpha channel, if the underlying image has one. I fixed it by replicating the first/last row/column values if accessing values outside the boundaries.

from resize.