PNG：无损与透明PNG: Lossless & Transparency
学习目标LEARNING OBJECTIVES
PNG 是无损的图片格式，还支持透明——什么时候用它，为什么不能拿它当视频素材？
概念说明CONCEPTS
无损压缩的图片格式——压缩后每个像素原样保留，一条信息不丢；还支持透明通道（alpha），背景可以透明。
什么时候用：图标、字幕条、带字图形、透明底素材、截图——凡是「图形」或「带字」的都归它。
操作步骤STEPS
- 图标、字幕条、带字图形，导出成 PNG
- 需要透明底就带上 alpha 通道
- 视频序列不要用 PNG——一帧一个文件，合成用 DPX / EXR
练习PRACTICE
动手任务
把同一张带透明底的图形分别存成 PNG 和 JPG，看透明还保不保。
自检清单
做完任务后逐条自查，全部能打勾才算过。 做完任务后逐条自查，全部能打勾才算过。
常见问题FAQ
PNG 能当视频素材吗？
不能——体积太大，一帧一个文件；序列素材用 DPX / EXR。
PNG 用在哪些地方？
图标、字幕条、带字图形、透明底素材、截图——凡是「图形」或「带字」的都归它。
Learning Objectives学习目标
PNG is a lossless still format with transparency — when do you use it, and why never as video footage?
Concepts概念说明
A lossless image format — after compression every pixel is exactly as it was, nothing lost; it also carries an alpha channel for transparency.
When to use it: icons, lower thirds, graphics with text, transparent elements, screenshots — anything that is a graphic or carries text.
Steps操作步骤
- Export icons, lower thirds and text graphics as PNG
- Keep the alpha channel when you need transparency
- Never as film sequences — compositing uses DPX / EXR
Practice练习
Hands-on task
Save the same transparent graphic as PNG and as JPG, and check whether the transparency survives.
Self-check
Work through the task, then tick every line; all checked means you own this card. Work through the task, then tick every line; all checked means you own this card.
FAQ常见问题
Can PNG be used as video footage?
No — far too heavy, one file per frame; sequences use DPX / EXR.
Where does PNG belong?
Icons, lower thirds, text graphics, transparent assets, screenshots — anything graphic or carrying text.