Changing the resolution (DPI) using ImageMagick

Converting the .tga format into .png:
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convert 1C1Y_snap.tga test.png
Changing its DPI from 72 dots per inch to 300 dots per inch:
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convert test.png -set units PixelsPerInch -density 300 test_3.png

Reference: ImageMagick
Reference: Using Photoshop Elements