Problem in Compressing textures with PVRTC

When I use PVRTC format to compress my .png files, I found a strange things that if there were any color in one side of a texture, it will show some strange color in other side after compressing.For pic1, you can see some color in the left side of the texture, it disappeared in pic2 after i delete the 1pixcel width color in the right side. any one can tell me what’s really going on? i think this may be a bug of unity,and it can be avoid by modify the algorithm of pvrtc compressing

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In the texture settings, do you have the repeat option set to clamp or repeat? If it’s set to repeat, you may see these artifacts with any mesh that’s UVs go to the full extents of the texture, and compression often just exacerbates the effect.