如何制作Webp文件
如何制作Webp文件
一、什么是Webp
二、Webp文件制作准备
三、Jpg或png转换到Webp方法
四、Webp文件转换成png/ppm/pgm文件
五、在PC上查看webp文件
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一、什么是Webp
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WebP是Google新推出的影像技术，它可让网页图档有效进行压缩，同时在质量相同的情况下，WebP格式图像的体积要比JPEG格式图像小40%，进而让整体网页下载速度加快。为了改善JPEG的图片压缩技术，他们使用了一种基于VP8编码(已在2010五月开源)的图片压缩器，利用预测编码技术，同时还采用了一种基于RIFF的非常轻量级的容器。这种容器只会给每张图片增加20字节，但能让图片作者保存他们想要存储的元数据。
与JPEG相同，WebP是一种有损压缩利用预测编码技术。
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二、Webp文件制作准备
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Google开发并放出了不同操作系统的WebP文件解码器(libvpx)和命令行工具(webpconv)。
下载地址：http://code.google.com/intl/zh-CN/speed/webp/download.html
我下载了用于Windows的WebpCodecSetup.exe 和libwebp-0.1.3-windows-x86.zip
1. 先安装WebpCodecSetup.exe，
2. 解压libwebp-0.1.3-windows-x86.zip（无需安装）
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三、Jpg或png转换到Webp方法
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进入libwebp-0.1.3-windows-x86.zip的解压目录，可以看到cwebp.exe和dwebp.exe，其中cwebp.exe是将jpg或png文件转换成webp文件，dwebp.exe是将webp文件转换成png、pp或pgm。这两个程序只能在dos命令行环境下运行
1. 点击“开始”->“运行”->输入 cmd 后回车进入dos环境
2. 输入路径进入解压文件夹，以下是我安装的路径
C:\Documents andSettings\Administrator>e:
E:\>cd libwebp-0.1.3-windows-x86
E:\libwebp-0.1.3-windows-x86>
3. 输入命令，将jpg或png转换成webp
命令行结构：cwebp [-preset <...>] [options] in_file [-o out_file]
E:\libwebp-0.1.3-windows-x86> cwebp -qquality e:\photo\png1.png -o e:\webp1.webp （回车）
（e:\photo\png1.png是原文件路径，e:\webp1.webp是目标文件路径）
Saving file ' webp1.webp'
27672 bytes Y-U-V-All-PSNR 30.30 32.22 32.78 30.91 dB
block count: intra4: 1372
intra16: 10378 (-> 88.32%)
skipped block: 6204 (52.80%)
bytes used: header: 131 (0.5%)
mode-partition: 13138 (47.5%)
Residuals bytes |segment 1|segment 2|segment 3|segment4| total
intra4-coeffs: | 3918 | 911 | 268 | 65 | 5162 (18.7%)
intra16-coeffs: | 3086 | 1964 | 881 | 240 | 6171 (22.3%)
chroma coeffs: | 1627 | 902 | 408 | 105 | 3042 (11.0%)
macroblocks: | 27%| 33%| 26%| 12%| 11750
quantizer: | 127 | 127 | 127 | 127 |
filter level: | 19 | 14| 11| 9 |
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segments total: | 8631 | 3777 | 1557 | 410 | 14375 (51.9%)
4. 转换成功，在E:\libwebp-0.1.3-windows-x86目录中会生成一个webp1.webp文件
5. cwebp通过不同命令的选项，可以对图片的大小、尺寸打印信息等进行设置。
E:\libwebp-0.1.3-windows-x86>cwebp.exe –H（回车）
options:
-h / -help ............ short help
-H / -longhelp ........ long help
-q <float> ............. qualityfactor (0:small..100:big)
-preset <string> ....... Presetsetting, one of:
default, photo, picture,
drawing, icon, text
-preset must come first, as it overwritesother parameters.
-m <int> ............... compressionmethod (0=fast, 6=slowest)
-segments <int> ........ number ofsegments to use (1..4)
-s <int> <int> ......... Inputsize (width x height) for YUV
-sns <int> ............. SpatialNoise Shaping (0:off, 100:max)
-f <int> ............... filterstrength (0=off..100)
-sharpness <int> ....... filtersharpness (0:most .. 7:least sharp)
-strong ................ use strong filterinstead of simple.
-partition_limit <int> . limitquality to fit the 512k limit on the first partition (0=no degradation ...100=full)
-pass <int> ............ analysispass number (1..10)
-partitions <int> ...... number ofpartitions to use (0..3)
-crop <x> <y> <w><h> .. crop picture with the given rectangle
-resize <w> <h> ........ resizepicture (after any cropping)
-map <int> ............. print map ofextra info.
-d <file.pgm> .......... dump thecompressed output (PGM file).
-short ................. condense printedmessage
-quiet ................. don't printanything.
-version ............... print versionnumber and exit.
-noasm ................. disable allassembly optimizations.
-v ..................... verbose, e.g.print encoding/decoding times
Experimental Options:
-size <int> ............ Target size(in bytes)
-psnr <float> .......... Target PSNR(in dB. typically: 42)
-af <int> .............. adjustfilter strength (0=off, 1=on)
-pre <int> .............pre-processing filter
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四、Webp文件转换成png/ppm/pgm文件
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通过dwebp命令可以将Webp文件转换成png/ppm/pgm文件
1. 点击“开始”->“运行”->输入 cmd 后回车进入dos环境
2. 输入路径进入解压文件夹，以下是我安装的路径
C:\Documents andSettings\Administrator>e:
E:\>cd libwebp-0.1.3-windows-x86
E:\libwebp-0.1.3-windows-x86>
3. 输入命令，将Webp转换成png/ppm/pgm
Webp to png
E:\libwebp-0.1.3-windows-x86>dwebpwebp1.webp –o png1.png
Decoded webp1.webp. Dimensions: 2000 x1500. Now saving...
Saved file png1.png
转换成功，在E:\libwebp-0.1.3-windows-x86目录中会生成一个png1.png文件
Webp to ppm
E:\libwebp-0.1.3-windows-x86>dwebpwebp1.webp –ppm –o ppm1.ppm
Decoded webp1.webp. Dimensions: 2000 x1500. Now saving...
Saved file ppm1.ppm
转换成功，在E:\libwebp-0.1.3-windows-x86目录中会生成一个ppm1.ppm文件
Webp to pgm
E:\libwebp-0.1.3-windows-x86>dwebpwebp1.webp –ppm –o ppm1.pgm
Decoded webp1.webp. Dimensions: 2000 x1500. Now saving...
Saved file pgm1.pgm
转换成功，在E:\libwebp-0.1.3-windows-x86目录中会生成一个pgm1.ppm文件
4. dwebp通过不同命令的选项，可以对图片进行一些设置。
E:\libwebp-0.1.3-windows-x86>dwebp.exe –H（回车）
Options:
-ppm ......... save the raw RGB samples ascolor PPM
-pgm ......... save the raw YUV samples asa grayscale PGM
file with IMC4 layout.
Other options are:
-version .... print version number and exit.
-nofancy ..... don't use the fancy YUV420upscaler.
-nofilter .... disable in-loop filtering.
-mt .......... use multi-threading
-crop <x> <y> <w><h> ... crop output with the given rectangle
-scale <w> <h> .......... scalethe output (*after* any cropping)
-h ....... this help message.
-v ....... verbose (e.g. print encoding/decoding times)
-noasm ....... disable all assemblyoptimizations.
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五、在PC上查看webp文件
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1. 安装Google chrome浏览器
安装后打开chrome浏览器，然后将webp文件直接拖到浏览器中
2. 安装chrome内嵌框架插件
地址：http://code.google.com/intl/zh-CN/speed/webp/
点击“接收并激活”开始在线安装