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305911是什么?就是一个数学表达式,也就是0.3R+0.59G+0.11B。在photoshop中,它究竟是计算什么的一个数学表达式?有人说是lab中的明度;也有人说它是灰度模式中的灰度;也有人说它是RGB模式中的亮度(也就是直方图中的亮度)。这对操作者来讲研究它意义并不大,图像的操作有更多的主观成份。但对研究者来讲,弄清它究竟是什么,却是必要的。公式本身就是一个固定的定义而已,没有什么需要特别说明的。下面只是通过验证的办法来说明它究竟应该归属于明度、灰度还是亮度。验证它的归属前,先把0.3R+0.59G+0.11B这个表达式具体到一幅图像上并把它计算出来。先做一下准备工作。把红、绿、蓝通道复制到图层上来。 <BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/8/83/83F6EFEEDC80DCB26CBB4B76B9CF07FD.jpg')" alt="" src="http://cimg2.163.com/catchpic/8/83/83F6EFEEDC80DCB26CBB4B76B9CF07FD.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0><BR><BR>把0。3R换算成色阶值,0。3×255=76。5,取整为77。再如图操作。 <BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/B/BF/BFDA4A916163E2BD3C93D672D59FDC63.jpg')" alt="" src="http://cimg2.163.com/catchpic/B/BF/BFDA4A916163E2BD3C93D672D59FDC63.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0>合并图层并关闭。把0。59G换算成色阶,0。59×255=150。45,取整为150。再如图操作。 <BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/3/37/3728826E3313B22D2249FC24D4332DF3.jpg')" alt="" src="http://cimg2.163.com/catchpic/3/37/3728826E3313B22D2249FC24D4332DF3.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0><BR><BR>合并图层并关闭。把0。11B换算成色阶,0。11×255=28。05,取整为28。再如图操作。 <BR><BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/D/DF/DF2B408E617B0A5F3DD1ADD860BD1BC5.jpg')" alt="" src="http://cimg2.163.com/catchpic/D/DF/DF2B408E617B0A5F3DD1ADD860BD1BC5.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0><BR><BR>然后将红通道图层、绿通道图层的图层混合模式改为“线性减淡”。线性减淡就是相加,把三个图层同一像素点的值加在一起。 <BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/D/D8/D8665AA9CEE697B98B34DAB6D57D2F08.jpg')" alt="" src="http://cimg2.163.com/catchpic/D/D8/D8665AA9CEE697B98B34DAB6D57D2F08.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0>将三个通道图层合并。我给它改了一个名字叫:0.3r0.59g0.11b。这个0.3r0.59g0.11b图层就是我们所说的上面的数学表达式了。到此准备工作完成,下面进行验证。 <BR><BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/E/E4/E451EECDC7BE28C04A777A982E083428.jpg')" alt="" src="http://cimg2.163.com/catchpic/E/E4/E451EECDC7BE28C04A777A982E083428.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0><BR><BR>验证: <BR>打开直方图,“通道”改为“亮度”。注意看直方图及其以下有红框的一组数据。 <BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/C/C4/C46F3EFFC8BFBA6B9D2E1DD53D220C3E.jpg')" alt="" src="http://cimg2.163.com/catchpic/C/C4/C46F3EFFC8BFBA6B9D2E1DD53D220C3E.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0><BR><BR>关闭上一图层的眼睛,“通道”改为“亮度”。注意看直方图及其以下有红框的一组数据。并与楼上的直方图进行比较。可以看出,基本相同,数据上的小出入是计算上的误差。 <BR><BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/E/E8/E85805D3BC6E74B2D84260A9775A34C6.jpg')" alt="" src="http://cimg2.163.com/catchpic/E/E8/E85805D3BC6E74B2D84260A9775A34C6.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0>以上是对整个图像的直方图的比较,下面取图像上的一点作比较。打开上层图像的眼睛,取一个颜色点,注意信息面板上的数据。 <BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/9/9A/9A400668187D090ED82FE34D75744F0D.jpg')" alt="" src="http://cimg2.163.com/catchpic/9/9A/9A400668187D090ED82FE34D75744F0D.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0><BR><BR>关闭上一图层的眼睛,关闭上层图像的眼睛,用信息面板上的数据作计算:0。3×238+0。59×190+0。11×144=199。34,取整为199。 <BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/D/D3/D39D10B7C9CB88709A2C7CB7B758B929.jpg')" alt="" src="http://cimg2.163.com/catchpic/D/D3/D39D10B7C9CB88709A2C7CB7B758B929.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0><BR><BR>我们再来把图像转为Lab模式。上层已经不需要了,关闭或删除。打开直方图查看下层的明度。注意直方图与数据,并与10楼的直方图及数据比较,可以看出差别很大,这绝不是误差能够解释的。 <BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/3/39/393D60FFA1B4EE04253D424DB1FAFCE5.jpg')" alt="" src="http://cimg2.163.com/catchpic/3/39/393D60FFA1B4EE04253D424DB1FAFCE5.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0>在通道面板中点选明度通道,看设置的颜色点的数据是216,明显不等于用公式0.3R+0.59G+0.11B计算出的值199。34。 <BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/F/F5/F57F08EB64CD1B2C8A4398532D19D8CD.jpg')" alt="" src="http://cimg2.163.com/catchpic/F/F5/F57F08EB64CD1B2C8A4398532D19D8CD.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0><BR><BR>比较一下lab的明度图与rgb的亮度图,差别显而易见。因此,0.3R+0.59G+0.11B应该是RGB模式下的亮度计算公式而不是lab模式下的明度计算公式。曾请教过凤兮版主,明度的计算公式很复杂,在此不提。 <BR><BR><IMG onmousewheel="return imgzoom(this)" onmouseover="attachimg(this, 'mouseover')" onclick="attachimg(this, 'click', 'http://cimg2.163.com/catchpic/8/89/89EA5AB2C21CB971343411D7D3DC43A5.jpg')" alt="" src="http://cimg2.163.com/catchpic/8/89/89EA5AB2C21CB971343411D7D3DC43A5.jpg" onload="attachimg(this, 'load', 'Click here to open new window\nCTRL+Mouse wheel to zoom in/out')" border=0><BR><script language="JavaScript" src="http://www.16xx8.com/bbs/10.js"></script><BR> |
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