April 2020
Intermediate to advanced
210 pages
4h 47m
Chinese
Content preview from 数据压缩入门
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152
｜
第
12
章
12.1.3
让想法真正工作
显然，为了让用户感受到相同的视觉品质，不同类型的图像需要有不同的输出设定。一
张森林的照片由于有很多边缘和不同的颜色，因此需要更多的二进制位以充分地展示它；
而一张手绘的卡通，因为其颜色简单，所以不会产生很多的渐变问题。因此，不同的图
像类型，需要使用不同的输出设定。然而，如何在开发环境中实现它，这个问题留给你
来解决。
显而易见，通过云端的计算资源反复寻找找出理想的质量设定是最简单的方法，但并不是
所有的开发人员都有时间和经费做到这一点。
12.2
图像的尺寸很重要
在现今的移动世界，有很多屏幕尺寸不同、处理能力各异的设备。这对开发人员来说是一
个很大问题：在处理图像时应该使用什么样的分辨率？
考虑这样一个场景，一位用户正在用手机上传一张
800
万像素的照片。
5
对那些屏幕分辨率与上传用户相同的用户来说，有理由相信他们希望看到的是同样大小的
照片，可是应该如何应对那些屏幕分辨率只有一半或者四分之一的用户呢？这与从桌面显
示器上和手机屏幕上看图像时的差别类似。显然，更小的屏幕会使用更小的物理像素显示
图像，因为它拥有的物理像素就少，那么应该在什么地方调整大小呢？
将全分辨率的图像发送到设备上，在渲染前再调整大小，对开发人员来说，这样做肯定最
省事，但缺点也很明显，我们将用户不需要（也不会看）的数据发给了他们。这样做，其
实是把钱往水里扔，还听不到一个响。
更好的方法是直接在云端调整图像的大小，或者在某处缓存调整大小后的图像，这样就能
向小屏幕发送小尺寸的图像。这并非遥不可及。很有可能 ...
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I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.