Using adb:
<div>
</div><div><div class="wp_codebox" style="background-color: #f9f9f9; border: 1px solid silver; color: #110000; font-family: 'Open Sans', sans-serif; font-size: 16px; line-height: 25.8799991607666px; margin: 0px 0px 0.5em; outline: 0px; overflow: auto; padding: 0px; vertical-align: baseline; width: 716.760437011719px;"><table style="border-collapse: collapse; border-spacing: 0px; border: none; font-family: inherit; font-size: 16px; font-style: inherit; font-weight: inherit; margin: 0px !important; outline: 0px; padding: 0px; vertical-align: baseline; width: 716.666687011719px;"><tbody style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><tr id="p561073" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td class="code" id="p56107code3" style="border: 0px; font-family: inherit; font-style: inherit; margin: 0px; outline: 0px; padding: 2px 4px; vertical-align: top;"><pre class="shell" style="background: none; border: none; clear: none; float: none; font-size: 12px; font-style: inherit; font-weight: inherit; line-height: 1.333; outline: 0px; overflow: visible; padding: 0px; vertical-align: baseline; white-space: pre-wrap; width: auto; word-wrap: break-word;">adb shell wm size 640x480</pre></td></tr></tbody></table></div><div class="wp_codebox" style="background-color: #f9f9f9; border: 1px solid silver; color: #110000; font-family: 'Open Sans', sans-serif; font-size: 16px; line-height: 25.8799991607666px; margin: 0px 0px 0.5em; outline: 0px; overflow: auto; padding: 0px; vertical-align: baseline; width: 716.760437011719px;"><table style="border-collapse: collapse; border-spacing: 0px; border: none; font-family: inherit; font-size: 16px; font-style: inherit; font-weight: inherit; margin: 0px !important; outline: 0px; padding: 0px; vertical-align: baseline; width: 716.666687011719px;"><tbody style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><tr id="p561074" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td class="code" id="p56107code4" style="border: 0px; font-family: inherit; font-style: inherit; margin: 0px; outline: 0px; padding: 2px 4px; vertical-align: top;"><pre class="shell" style="background: none; border: none; clear: none; float: none; font-size: 12px; font-style: inherit; font-weight: inherit; line-height: 1.333; outline: 0px; overflow: visible; padding: 0px; vertical-align: baseline; white-space: pre-wrap; width: auto; word-wrap: break-word;">adb shell wm density 160</pre></td></tr></tbody></table></div></div><div>
</div><div>Reset to defaults:</div><div>
</div><div><div class="wp_codebox" style="background-color: #f9f9f9; border: 1px solid silver; color: #110000; font-family: 'Open Sans', sans-serif; font-size: 16px; line-height: 25.8799991607666px; margin: 0px 0px 0.5em; outline: 0px; overflow: auto; padding: 0px; vertical-align: baseline; width: 716.760437011719px;"><table style="border-collapse: collapse; border-spacing: 0px; border: none; font-family: inherit; font-size: 16px; font-style: inherit; font-weight: inherit; margin: 0px !important; outline: 0px; padding: 0px; vertical-align: baseline; width: 716.666687011719px;"><tbody style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><tr id="p561075" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td class="code" id="p56107code5" style="border: 0px; font-family: inherit; font-style: inherit; margin: 0px; outline: 0px; padding: 2px 4px; vertical-align: top;"><pre class="shell" style="background: none; border: none; clear: none; float: none; font-size: 12px; font-style: inherit; font-weight: inherit; line-height: 1.333; outline: 0px; overflow: visible; padding: 0px; vertical-align: baseline; white-space: pre-wrap; width: auto; word-wrap: break-word;">adb shell wm size reset</pre></td></tr></tbody></table></div><div class="wp_codebox" style="background-color: #f9f9f9; border: 1px solid silver; color: #110000; font-family: 'Open Sans', sans-serif; font-size: 16px; line-height: 25.8799991607666px; margin: 0px 0px 0.5em; outline: 0px; overflow: auto; padding: 0px; vertical-align: baseline; width: 716.760437011719px;"><table style="border-collapse: collapse; border-spacing: 0px; border: none; font-family: inherit; font-size: 16px; font-style: inherit; font-weight: inherit; margin: 0px !important; outline: 0px; padding: 0px; vertical-align: baseline; width: 716.666687011719px;"><tbody style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><tr id="p561076" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td class="code" id="p56107code6" style="border: 0px; font-family: inherit; font-style: inherit; margin: 0px; outline: 0px; padding: 2px 4px; vertical-align: top;"><pre class="shell" style="background: none; border: none; clear: none; float: none; font-size: 12px; font-style: inherit; font-weight: inherit; line-height: 1.333; outline: 0px; overflow: visible; padding: 0px; vertical-align: baseline; white-space: pre-wrap; width: auto; word-wrap: break-word;">adb shell wm density reset</pre></td></tr></tbody></table></div></div><div>
</div><div>
</div><div>Source (Ray Wenderlich)</div>
read