膠印印前課件-網(wǎng)點(diǎn)形狀和網(wǎng)點(diǎn)面積率之選擇與決策

膠印印前處理

－網(wǎng)點(diǎn)形狀和網(wǎng)點(diǎn)面積率網(wǎng)點(diǎn)面積率與網(wǎng)點(diǎn)周長(zhǎng)之間的變化關(guān)系：網(wǎng)點(diǎn)面積率與網(wǎng)點(diǎn)周長(zhǎng)并非同向增減，會(huì)在某個(gè)臨界點(diǎn)后將出現(xiàn)反向增減。臨界點(diǎn)為網(wǎng)點(diǎn)是否與網(wǎng)格出現(xiàn)接觸，又稱(chēng)搭角。搭角現(xiàn)象將極大改變網(wǎng)點(diǎn)影響力。選擇與決策網(wǎng)點(diǎn)形狀方形網(wǎng)點(diǎn)：加網(wǎng)線數(shù)L為常數(shù)ab50%<50%>50%網(wǎng)點(diǎn)形狀-方形網(wǎng)點(diǎn)選擇與決策a網(wǎng)點(diǎn)面積率對(duì)周長(zhǎng)的變化率為同向增減。網(wǎng)點(diǎn)面積率對(duì)周長(zhǎng)的變化率為反向增減。50%網(wǎng)點(diǎn)形狀-方形網(wǎng)點(diǎn)選擇與決策=78.5%rr>78.5%r<78.5%r

網(wǎng)點(diǎn)面積率對(duì)周長(zhǎng)的變化率在78.5%處為分界點(diǎn)。網(wǎng)點(diǎn)形狀-圓形網(wǎng)點(diǎn)選擇與決策網(wǎng)點(diǎn)形狀-圓形網(wǎng)點(diǎn)選擇與決策圓形網(wǎng)點(diǎn)與方形網(wǎng)點(diǎn)的區(qū)別50%<50%>50%>78.5%r<50%r

50%78.5%網(wǎng)點(diǎn)形狀選擇與決策在網(wǎng)點(diǎn)未搭角并且方形網(wǎng)點(diǎn)與圓形網(wǎng)點(diǎn)面積率相等時(shí),pr

57%在網(wǎng)點(diǎn)未搭角且<57%，方形網(wǎng)點(diǎn)的網(wǎng)點(diǎn)擴(kuò)大趨勢(shì)比圓形網(wǎng)點(diǎn)高。網(wǎng)點(diǎn)形狀選擇與決策網(wǎng)點(diǎn)的搭接會(huì)引起：密度的跳躍性升高。網(wǎng)點(diǎn)形狀不同，相鄰網(wǎng)點(diǎn)搭接的網(wǎng)點(diǎn)面積率不同、

搭接的次數(shù)也不同，圖像階調(diào)傳遞的狀況不同。純粹的方形網(wǎng)點(diǎn)在50%一次搭角，純粹的圓形網(wǎng)點(diǎn)在78.5%

搭角，橢圓形網(wǎng)點(diǎn)在大約40%

第1次搭角，大約60%

第2次搭角。網(wǎng)點(diǎn)形狀選擇與決策網(wǎng)點(diǎn)形狀選擇與決策風(fēng)景畫(huà)，強(qiáng)調(diào)反差，需要階調(diào)跳躍最好是出現(xiàn)在中間調(diào)區(qū)；人物肖像，強(qiáng)調(diào)過(guò)渡的均勻性，階調(diào)跳躍最好是避開(kāi)中間調(diào)區(qū)域；亮中調(diào)區(qū)域細(xì)膩柔和，暗調(diào)層次少的圖像。方形點(diǎn)菱形或橢圓點(diǎn)圓形點(diǎn)網(wǎng)點(diǎn)形狀選擇與決