ImageMagick:PNG的无损最大压缩？

我想在使用ImageMagick保存到无损PNG时实现最大压缩量。我正在对许多PSD进行批量转换

我尝试了一些方法，但在我看来，生成的PNG图像不如原始图像清晰，尽管我妻子看不见

以下是我正在使用的当前论点：

convert -depth 24 -define png:compression-filter=1 \ 
  -define png:compression-level=9 -define png:compression-strategy=2 

根据：

及

这意味着：

• 压缩过滤器为1（子）
• 最大压缩级别9
• 压缩策略仅为2 huffman_（因此无过滤，尽管此压缩过滤器应为无损）

根据文档：“有效值为0到4，表示默认、过滤、仅huffman_、rle和固定的ZLIB压缩策略。如果您使用的是不支持Z_-rle（1.2.0之前）或Z_-fixed（1.2.2.2之前）的旧ZLIB，则值3和4将分别使用ZLIB默认策略。”

顺便说一句，我的图像是960x720像素

（如果我使用默认的压缩策略0，我会得到大文件。可能是9的压缩过滤器和0的压缩策略产生了更小的图像，但我仍然不确定它是否是无损的）

问题:

这是无损压缩吗？如果没有，错误在哪里

你知道如何实现更好的无损压缩吗

---

我认为您已经达到或超过了ImageMagick文档的极限，并建议您根据经验得出答案——或者，如果您确实得到了一个确定的答案，您至少要根据经验进行测试

我无法访问您的图像，因此我自己生成了一个参考图像，如下所示。它包含一个容易压缩的纯色块（红色）、一个黑白渐变和一堆噪音，因此有一些东西可以让大多数类型的压缩感到高兴或不高兴

为了测试您是否有无损压缩，我建议您将图像转换为

PPM

格式-请参阅。它不包含日期、时间、统计数据或任何内容，只包含极其简单格式的纯图像数据和大小，从而允许比较像素值是否通过压缩发生了变化

然后我编写了一个脚本，如下所示，使用所有可能的过滤器、策略和级别压缩参考图像，以查看文件大小，以及它们是否遭受任何损失，因此与参考

PPM

图像不同：

以下是脚本：

#!/bin/bash
convert -depth 24 -size 200x200 xc:red gradient:black-white \( xc:white +noise random \) +append reference.png
convert reference.png reference.ppm
for f in {0..5}; do
   for l in {0..9}; do
      for s in {0..4}; do
         outfile="out_${f}_${l}_${s}.png"
         convert reference.png -define png:compression-filter=$f -define png:compression-level=$l -define png:compression-strategy=$s "$outfile"
         size=$(OSXFileSize "$outfile")
         echo filter:$f, level:$l, strategy:$s, size:$size
         convert "$outfile" "$outfile.ppm"
         diff "$outfile.ppm" reference.ppm
      done
   done
done

所有文件都进行了相同的比较，因此我使用的任何参数似乎都没有任何压缩损失。尺寸如下：

filter:0, level:0, strategy:0, size:720796
filter:0, level:0, strategy:1, size:720796
filter:0, level:0, strategy:2, size:720801
filter:0, level:0, strategy:3, size:718136
filter:0, level:0, strategy:4, size:720796
filter:0, level:1, strategy:0, size:246377
filter:0, level:1, strategy:1, size:246377
filter:0, level:1, strategy:2, size:524864
filter:0, level:1, strategy:3, size:517549
filter:0, level:1, strategy:4, size:259348
filter:0, level:2, strategy:0, size:246377
filter:0, level:2, strategy:1, size:246377
filter:0, level:2, strategy:2, size:524864
filter:0, level:2, strategy:3, size:517549
filter:0, level:2, strategy:4, size:259348
filter:0, level:3, strategy:0, size:246377
filter:0, level:3, strategy:1, size:246377
filter:0, level:3, strategy:2, size:524864
filter:0, level:3, strategy:3, size:517549
filter:0, level:3, strategy:4, size:259348
filter:0, level:4, strategy:0, size:244894
filter:0, level:4, strategy:1, size:244859
filter:0, level:4, strategy:2, size:524864
filter:0, level:4, strategy:3, size:517549
filter:0, level:4, strategy:4, size:258039
filter:0, level:5, strategy:0, size:244916
filter:0, level:5, strategy:1, size:244881
filter:0, level:5, strategy:2, size:524864
filter:0, level:5, strategy:3, size:517549
filter:0, level:5, strategy:4, size:258064
filter:0, level:6, strategy:0, size:244916
filter:0, level:6, strategy:1, size:244881
filter:0, level:6, strategy:2, size:524864
filter:0, level:6, strategy:3, size:517549
filter:0, level:6, strategy:4, size:258064
filter:0, level:7, strategy:0, size:244916
filter:0, level:7, strategy:1, size:244881
filter:0, level:7, strategy:2, size:524864
filter:0, level:7, strategy:3, size:517549
filter:0, level:7, strategy:4, size:258064
filter:0, level:8, strategy:0, size:244433
filter:0, level:8, strategy:1, size:244405
filter:0, level:8, strategy:2, size:524864
filter:0, level:8, strategy:3, size:517549
filter:0, level:8, strategy:4, size:257674
filter:0, level:9, strategy:0, size:244433
filter:0, level:9, strategy:1, size:244405
filter:0, level:9, strategy:2, size:524864
filter:0, level:9, strategy:3, size:517549
filter:0, level:9, strategy:4, size:257674
filter:1, level:0, strategy:0, size:720796
filter:1, level:0, strategy:1, size:720796
filter:1, level:0, strategy:2, size:720801
filter:1, level:0, strategy:3, size:286904
filter:1, level:0, strategy:4, size:720796
filter:1, level:1, strategy:0, size:247643
filter:1, level:1, strategy:1, size:247643
filter:1, level:1, strategy:2, size:331829
filter:1, level:1, strategy:3, size:245708
filter:1, level:1, strategy:4, size:260505
filter:1, level:2, strategy:0, size:247375
filter:1, level:2, strategy:1, size:247375
filter:1, level:2, strategy:2, size:331829
filter:1, level:2, strategy:3, size:245708
filter:1, level:2, strategy:4, size:260452
filter:1, level:3, strategy:0, size:247375
filter:1, level:3, strategy:1, size:247375
filter:1, level:3, strategy:2, size:331829
filter:1, level:3, strategy:3, size:245708
filter:1, level:3, strategy:4, size:260452
filter:1, level:4, strategy:0, size:245515
filter:1, level:4, strategy:1, size:245489
filter:1, level:4, strategy:2, size:331829
filter:1, level:4, strategy:3, size:245708
filter:1, level:4, strategy:4, size:258810
filter:1, level:5, strategy:0, size:245544
filter:1, level:5, strategy:1, size:245519
filter:1, level:5, strategy:2, size:331829
filter:1, level:5, strategy:3, size:245708
filter:1, level:5, strategy:4, size:258835
filter:1, level:6, strategy:0, size:245597
filter:1, level:6, strategy:1, size:245570
filter:1, level:6, strategy:2, size:331829
filter:1, level:6, strategy:3, size:245708
filter:1, level:6, strategy:4, size:258885
filter:1, level:7, strategy:0, size:245597
filter:1, level:7, strategy:1, size:245570
filter:1, level:7, strategy:2, size:331829
filter:1, level:7, strategy:3, size:245708
filter:1, level:7, strategy:4, size:258885
filter:1, level:8, strategy:0, size:245251
filter:1, level:8, strategy:1, size:245230
filter:1, level:8, strategy:2, size:331829
filter:1, level:8, strategy:3, size:245708
filter:1, level:8, strategy:4, size:258587
filter:1, level:9, strategy:0, size:245267
filter:1, level:9, strategy:1, size:245254
filter:1, level:9, strategy:2, size:331829
filter:1, level:9, strategy:3, size:245708
filter:1, level:9, strategy:4, size:258589
filter:2, level:0, strategy:0, size:720796
filter:2, level:0, strategy:1, size:720796
filter:2, level:0, strategy:2, size:720801
filter:2, level:0, strategy:3, size:628470
filter:2, level:0, strategy:4, size:720796
filter:2, level:1, strategy:0, size:246114
filter:2, level:1, strategy:1, size:246114
filter:2, level:1, strategy:2, size:439545
filter:2, level:1, strategy:3, size:358177
filter:2, level:1, strategy:4, size:258999
filter:2, level:2, strategy:0, size:246114
filter:2, level:2, strategy:1, size:246114
filter:2, level:2, strategy:2, size:439545
filter:2, level:2, strategy:3, size:358177
filter:2, level:2, strategy:4, size:258999
filter:2, level:3, strategy:0, size:246114
filter:2, level:3, strategy:1, size:246114
filter:2, level:3, strategy:2, size:439545
filter:2, level:3, strategy:3, size:358177
filter:2, level:3, strategy:4, size:258999
filter:2, level:4, strategy:0, size:244701
filter:2, level:4, strategy:1, size:244679
filter:2, level:4, strategy:2, size:439545
filter:2, level:4, strategy:3, size:358177
filter:2, level:4, strategy:4, size:257722
filter:2, level:5, strategy:0, size:244721
filter:2, level:5, strategy:1, size:244700
filter:2, level:5, strategy:2, size:439545
filter:2, level:5, strategy:3, size:358177
filter:2, level:5, strategy:4, size:257744
filter:2, level:6, strategy:0, size:244727
filter:2, level:6, strategy:1, size:244704
filter:2, level:6, strategy:2, size:439545
filter:2, level:6, strategy:3, size:358177
filter:2, level:6, strategy:4, size:257744
filter:2, level:7, strategy:0, size:244727
filter:2, level:7, strategy:1, size:244704
filter:2, level:7, strategy:2, size:439545
filter:2, level:7, strategy:3, size:358177
filter:2, level:7, strategy:4, size:257744
filter:2, level:8, strategy:0, size:244340
filter:2, level:8, strategy:1, size:244322
filter:2, level:8, strategy:2, size:439545
filter:2, level:8, strategy:3, size:358177
filter:2, level:8, strategy:4, size:257436
filter:2, level:9, strategy:0, size:244155
filter:2, level:9, strategy:1, size:244130
filter:2, level:9, strategy:2, size:439545
filter:2, level:9, strategy:3, size:358177
filter:2, level:9, strategy:4, size:257298
filter:3, level:0, strategy:0, size:720796
filter:3, level:0, strategy:1, size:720796
filter:3, level:0, strategy:2, size:720801
filter:3, level:0, strategy:3, size:600694
filter:3, level:0, strategy:4, size:720796
filter:3, level:1, strategy:0, size:247741
filter:3, level:1, strategy:1, size:247741
filter:3, level:1, strategy:2, size:429487
filter:3, level:1, strategy:3, size:346943
filter:3, level:1, strategy:4, size:260468
filter:3, level:2, strategy:0, size:247711
filter:3, level:2, strategy:1, size:247711
filter:3, level:2, strategy:2, size:429487
filter:3, level:2, strategy:3, size:346943
filter:3, level:2, strategy:4, size:260444
filter:3, level:3, strategy:0, size:247463
filter:3, level:3, strategy:1, size:247463
filter:3, level:3, strategy:2, size:429487
filter:3, level:3, strategy:3, size:346943
filter:3, level:3, strategy:4, size:260331
filter:3, level:4, strategy:0, size:245681
filter:3, level:4, strategy:1, size:245659
filter:3, level:4, strategy:2, size:429487
filter:3, level:4, strategy:3, size:346943
filter:3, level:4, strategy:4, size:258797
filter:3, level:5, strategy:0, size:245685
filter:3, level:5, strategy:1, size:245663
filter:3, level:5, strategy:2, size:429487
filter:3, level:5, strategy:3, size:346943
filter:3, level:5, strategy:4, size:258796
filter:3, level:6, strategy:0, size:245686
filter:3, level:6, strategy:1, size:245665
filter:3, level:6, strategy:2, size:429487
filter:3, level:6, strategy:3, size:346943
filter:3, level:6, strategy:4, size:258796
filter:3, level:7, strategy:0, size:245686
filter:3, level:7, strategy:1, size:245665
filter:3, level:7, strategy:2, size:429487
filter:3, level:7, strategy:3, size:346943
filter:3, level:7, strategy:4, size:258796
filter:3, level:8, strategy:0, size:245474
filter:3, level:8, strategy:1, size:245458
filter:3, level:8, strategy:2, size:429487
filter:3, level:8, strategy:3, size:346943
filter:3, level:8, strategy:4, size:258628
filter:3, level:9, strategy:0, size:245508
filter:3, level:9, strategy:1, size:245491
filter:3, level:9, strategy:2, size:429487
filter:3, level:9, strategy:3, size:346943
filter:3, level:9, strategy:4, size:258639
filter:4, level:0, strategy:0, size:720796
filter:4, level:0, strategy:1, size:720796
filter:4, level:0, strategy:2, size:720801
filter:4, level:0, strategy:3, size:284043
filter:4, level:0, strategy:4, size:720796
filter:4, level:1, strategy:0, size:246892
filter:4, level:1, strategy:1, size:246892
filter:4, level:1, strategy:2, size:331489
filter:4, level:1, strategy:3, size:245305
filter:4, level:1, strategy:4, size:259428
filter:4, level:2, strategy:0, size:246299
filter:4, level:2, strategy:1, size:246299
filter:4, level:2, strategy:2, size:331489
filter:4, level:2, strategy:3, size:245305
filter:4, level:2, strategy:4, size:259021
filter:4, level:3, strategy:0, size:246316
filter:4, level:3, strategy:1, size:246316
filter:4, level:3, strategy:2, size:331489
filter:4, level:3, strategy:3, size:245305
filter:4, level:3, strategy:4, size:259026
filter:4, level:4, strategy:0, size:244335
filter:4, level:4, strategy:1, size:244259
filter:4, level:4, strategy:2, size:331489
filter:4, level:4, strategy:3, size:245305
filter:4, level:4, strategy:4, size:257491
filter:4, level:5, strategy:0, size:244343
filter:4, level:5, strategy:1, size:244260
filter:4, level:5, strategy:2, size:331489
filter:4, level:5, strategy:3, size:245305
filter:4, level:5, strategy:4, size:257494
filter:4, level:6, strategy:0, size:244350
filter:4, level:6, strategy:1, size:244262
filter:4, level:6, strategy:2, size:331489
filter:4, level:6, strategy:3, size:245305
filter:4, level:6, strategy:4, size:257500
filter:4, level:7, strategy:0, size:244350
filter:4, level:7, strategy:1, size:244262
filter:4, level:7, strategy:2, size:331489
filter:4, level:7, strategy:3, size:245305
filter:4, level:7, strategy:4, size:257500
filter:4, level:8, strategy:0, size:244282
filter:4, level:8, strategy:1, size:244251
filter:4, level:8, strategy:2, size:331489
filter:4, level:8, strategy:3, size:245305
filter:4, level:8, strategy:4, size:257461
filter:4, level:9, strategy:0, size:244321
filter:4, level:9, strategy:1, size:244284
filter:4, level:9, strategy:2, size:331489
filter:4, level:9, strategy:3, size:245305
filter:4, level:9, strategy:4, size:257473
filter:5, level:0, strategy:0, size:720796
filter:5, level:0, strategy:1, size:720796
filter:5, level:0, strategy:2, size:720801
filter:5, level:0, strategy:3, size:287526
filter:5, level:0, strategy:4, size:720796
filter:5, level:1, strategy:0, size:247117
filter:5, level:1, strategy:1, size:247117
filter:5, level:1, strategy:2, size:331910
filter:5, level:1, strategy:3, size:246241
filter:5, level:1, strategy:4, size:259811
filter:5, level:2, strategy:0, size:246903
filter:5, level:2, strategy:1, size:246903
filter:5, level:2, strategy:2, size:331910
filter:5, level:2, strategy:3, size:246241
filter:5, level:2, strategy:4, size:259757
filter:5, level:3, strategy:0, size:246976
filter:5, level:3, strategy:1, size:246976
filter:5, level:3, strategy:2, size:331910
filter:5, level:3, strategy:3, size:246241
filter:5, level:3, strategy:4, size:259742
filter:5, level:4, strategy:0, size:245005
filter:5, level:4, strategy:1, size:244969
filter:5, level:4, strategy:2, size:331910
filter:5, level:4, strategy:3, size:246241
filter:5, level:4, strategy:4, size:258135
filter:5, level:5, strategy:0, size:245025
filter:5, level:5, strategy:1, size:244985
filter:5, level:5, strategy:2, size:331910
filter:5, level:5, strategy:3, size:246241
filter:5, level:5, strategy:4, size:258149
filter:5, level:6, strategy:0, size:245056
filter:5, level:6, strategy:1, size:245009
filter:5, level:6, strategy:2, size:331910
filter:5, level:6, strategy:3, size:246241
filter:5, level:6, strategy:4, size:258176
filter:5, level:7, strategy:0, size:245056
filter:5, level:7, strategy:1, size:245009
filter:5, level:7, strategy:2, size:331910
filter:5, level:7, strategy:3, size:246241
filter:5, level:7, strategy:4, size:258176
filter:5, level:8, strategy:0, size:244838
filter:5, level:8, strategy:1, size:244841
filter:5, level:8, strategy:2, size:331910
filter:5, level:8, strategy:3, size:246241
filter:5, level:8, strategy:4, size:258009
filter:5, level:9, strategy:0, size:244857
filter:5, level:9, strategy:1, size:244857
filter:5, level:9, strategy:2, size:331910
filter:5, level:9, strategy:3, size:246241
filter:5, level:9, strategy:4, size:258009

convert wallpsw.png -resize 1024x768 -quality 95 \
                    -depth 8 wallpsw-q95-r1024x768-d8.png

很明显，你的数字会不同，因为你的图像不同，所以你必须看看什么对你的数据有效——但希望这将是一个起点

请注意，如果我按大小对上述内容进行排序，我会得到以下结果：

filter:2, level:9, strategy:1, size:244127
filter:2, level:9, strategy:0, size:244156
filter:4, level:8, strategy:1, size:244251
filter:4, level:4, strategy:1, size:244258
filter:4, level:5, strategy:1, size:244260
filter:4, level:6, strategy:1, size:244262
filter:4, level:7, strategy:1, size:244262
filter:4, level:8, strategy:0, size:244283
filter:4, level:9, strategy:1, size:244285
filter:2, level:8, strategy:1, size:244319
filter:4, level:9, strategy:0, size:244321
filter:4, level:4, strategy:0, size:244333
filter:2, level:8, strategy:0, size:244341
filter:4, level:5, strategy:0, size:244341
filter:4, level:6, strategy:0, size:244350
filter:4, level:7, strategy:0, size:244350
filter:0, level:8, strategy:1, size:244408
filter:0, level:9, strategy:1, size:244408
filter:0, level:8, strategy:0, size:244442
filter:0, level:9, strategy:0, size:244442
filter:2, level:4, strategy:1, size:244677
filter:2, level:5, strategy:1, size:244699
filter:2, level:4, strategy:0, size:244701
filter:2, level:6, strategy:1, size:244704
filter:2, level:7, strategy:1, size:244704
filter:2, level:5, strategy:0, size:244723
filter:2, level:6, strategy:0, size:244729
filter:2, level:7, strategy:0, size:244729
filter:5, level:8, strategy:1, size:244813
filter:5, level:8, strategy:0, size:244822
filter:5, level:9, strategy:1, size:244840
filter:5, level:9, strategy:0, size:244853
filter:0, level:4, strategy:1, size:244860
filter:0, level:5, strategy:1, size:244885
filter:0, level:6, strategy:1, size:244885
filter:0, level:7, strategy:1, size:244885
filter:0, level:4, strategy:0, size:244897
filter:0, level:5, strategy:0, size:244922
filter:0, level:6, strategy:0, size:244922
filter:0, level:7, strategy:0, size:244922
filter:5, level:4, strategy:1, size:244940
filter:5, level:5, strategy:1, size:244956
filter:5, level:6, strategy:1, size:244980
filter:5, level:7, strategy:1, size:244980
filter:5, level:4, strategy:0, size:244982
filter:5, level:5, strategy:0, size:245000
filter:5, level:6, strategy:0, size:245030
filter:5, level:7, strategy:0, size:245030
filter:1, level:8, strategy:1, size:245243
filter:1, level:9, strategy:1, size:245245
filter:1, level:8, strategy:0, size:245267
filter:1, level:9, strategy:0, size:245270
filter:4, level:1, strategy:3, size:245307
filter:4, level:2, strategy:3, size:245307
filter:4, level:3, strategy:3, size:245307
filter:4, level:4, strategy:3, size:245307
filter:4, level:5, strategy:3, size:245307
filter:4, level:6, strategy:3, size:245307
filter:4, level:7, strategy:3, size:245307
filter:4, level:8, strategy:3, size:245307
filter:4, level:9, strategy:3, size:245307
filter:3, level:8, strategy:1, size:245460
filter:5, level:1, strategy:3, size:245469
filter:5, level:2, strategy:3, size:245469
filter:5, level:3, strategy:3, size:245469
filter:5, level:4, strategy:3, size:245469
filter:5, level:5, strategy:3, size:245469
filter:5, level:6, strategy:3, size:245469
filter:5, level:7, strategy:3, size:245469
filter:5, level:8, strategy:3, size:245469
filter:5, level:9, strategy:3, size:245469
filter:3, level:8, strategy:0, size:245487
filter:3, level:9, strategy:1, size:245493
filter:1, level:4, strategy:1, size:245503
filter:3, level:9, strategy:0, size:245521
filter:1, level:4, strategy:0, size:245529
filter:1, level:5, strategy:1, size:245533
filter:1, level:5, strategy:0, size:245559
filter:1, level:6, strategy:1, size:245584
filter:1, level:7, strategy:1, size:245584
filter:1, level:6, strategy:0, size:245606
filter:1, level:7, strategy:0, size:245606
filter:3, level:4, strategy:1, size:245663
filter:3, level:5, strategy:1, size:245668
filter:3, level:6, strategy:1, size:245669
filter:3, level:7, strategy:1, size:245669
filter:3, level:4, strategy:0, size:245696
filter:3, level:5, strategy:0, size:245700
filter:3, level:6, strategy:0, size:245701
filter:3, level:7, strategy:0, size:245701
filter:1, level:1, strategy:3, size:245704
filter:1, level:2, strategy:3, size:245704
filter:1, level:3, strategy:3, size:245704
filter:1, level:4, strategy:3, size:245704
filter:1, level:5, strategy:3, size:245704
filter:1, level:6, strategy:3, size:245704
filter:1, level:7, strategy:3, size:245704
filter:1, level:8, strategy:3, size:245704
filter:1, level:9, strategy:3, size:245704
filter:2, level:1, strategy:0, size:245967
filter:2, level:1, strategy:1, size:245967
filter:2, level:2, strategy:0, size:245967
filter:2, level:2, strategy:1, size:245967
filter:2, level:3, strategy:0, size:245967
filter:2, level:3, strategy:1, size:245967
filter:4, level:2, strategy:0, size:246294
filter:4, level:2, strategy:1, size:246294
filter:4, level:3, strategy:0, size:246309
filter:4, level:3, strategy:1, size:246309
filter:0, level:1, strategy:0, size:246391
filter:0, level:1, strategy:1, size:246391
filter:0, level:2, strategy:0, size:246391
filter:0, level:2, strategy:1, size:246391
filter:0, level:3, strategy:0, size:246391
filter:0, level:3, strategy:1, size:246391
filter:4, level:1, strategy:0, size:246407
filter:4, level:1, strategy:1, size:246407
filter:5, level:2, strategy:0, size:246920
filter:5, level:2, strategy:1, size:246920
filter:5, level:1, strategy:0, size:246926
filter:5, level:1, strategy:1, size:246926
filter:5, level:3, strategy:0, size:246955
filter:5, level:3, strategy:1, size:246955
filter:1, level:2, strategy:0, size:247380
filter:1, level:2, strategy:1, size:247380
filter:1, level:3, strategy:0, size:247380
filter:1, level:3, strategy:1, size:247380
filter:3, level:1, strategy:0, size:247619
filter:3, level:1, strategy:1, size:247619
filter:3, level:2, strategy:0, size:247704
filter:3, level:2, strategy:1, size:247704
filter:3, level:3, strategy:0, size:247725
filter:3, level:3, strategy:1, size:247725
filter:1, level:1, strategy:0, size:247811
filter:1, level:1, strategy:1, size:247811
filter:2, level:9, strategy:4, size:257312
filter:2, level:8, strategy:4, size:257451
filter:4, level:8, strategy:4, size:257506
filter:4, level:9, strategy:4, size:257519
filter:4, level:4, strategy:4, size:257536
filter:4, level:5, strategy:4, size:257539
filter:4, level:6, strategy:4, size:257546
filter:4, level:7, strategy:4, size:257546
filter:0, level:8, strategy:4, size:257721
filter:0, level:9, strategy:4, size:257721
filter:2, level:4, strategy:4, size:257737
filter:2, level:5, strategy:4, size:257759
filter:2, level:6, strategy:4, size:257759
filter:2, level:7, strategy:4, size:257759
filter:5, level:8, strategy:4, size:258068
filter:5, level:9, strategy:4, size:258075
filter:0, level:4, strategy:4, size:258081
filter:0, level:5, strategy:4, size:258105
filter:0, level:6, strategy:4, size:258105
filter:0, level:7, strategy:4, size:258105
filter:5, level:4, strategy:4, size:258190
filter:5, level:5, strategy:4, size:258203
filter:5, level:6, strategy:4, size:258230
filter:5, level:7, strategy:4, size:258230
filter:3, level:8, strategy:4, size:258614
filter:1, level:8, strategy:4, size:258625
filter:1, level:9, strategy:4, size:258625
filter:3, level:9, strategy:4, size:258626
filter:3, level:5, strategy:4, size:258783
filter:3, level:6, strategy:4, size:258783
filter:3, level:7, strategy:4, size:258783
filter:3, level:4, strategy:4, size:258784
filter:1, level:4, strategy:4, size:258847
filter:1, level:5, strategy:4, size:258872
filter:1, level:6, strategy:4, size:258922
filter:1, level:7, strategy:4, size:258922
filter:2, level:1, strategy:4, size:258953
filter:2, level:2, strategy:4, size:258953
filter:2, level:3, strategy:4, size:258953
filter:4, level:2, strategy:4, size:259066
filter:4, level:3, strategy:4, size:259070
filter:4, level:1, strategy:4, size:259143
filter:0, level:1, strategy:4, size:259394
filter:0, level:2, strategy:4, size:259394
filter:0, level:3, strategy:4, size:259394
filter:5, level:3, strategy:4, size:259786
filter:5, level:2, strategy:4, size:259810
filter:5, level:1, strategy:4, size:259811
filter:3, level:1, strategy:4, size:260389
filter:3, level:2, strategy:4, size:260449
filter:3, level:3, strategy:4, size:260473
filter:1, level:2, strategy:4, size:260490
filter:1, level:3, strategy:4, size:260490
filter:1, level:1, strategy:4, size:260568
filter:4, level:0, strategy:3, size:284075
filter:5, level:0, strategy:3, size:284320
filter:1, level:0, strategy:3, size:286960
filter:4, level:1, strategy:2, size:331440
filter:4, level:2, strategy:2, size:331440
filter:4, level:3, strategy:2, size:331440
filter:4, level:4, strategy:2, size:331440
filter:4, level:5, strategy:2, size:331440
filter:4, level:6, strategy:2, size:331440
filter:4, level:7, strategy:2, size:331440
filter:4, level:8, strategy:2, size:331440
filter:4, level:9, strategy:2, size:331440
filter:5, level:1, strategy:2, size:331550
filter:5, level:2, strategy:2, size:331550
filter:5, level:3, strategy:2, size:331550
filter:5, level:4, strategy:2, size:331550
filter:5, level:5, strategy:2, size:331550
filter:5, level:6, strategy:2, size:331550
filter:5, level:7, strategy:2, size:331550
filter:5, level:8, strategy:2, size:331550
filter:5, level:9, strategy:2, size:331550
filter:1, level:1, strategy:2, size:331823
filter:1, level:2, strategy:2, size:331823
filter:1, level:3, strategy:2, size:331823
filter:1, level:4, strategy:2, size:331823
filter:1, level:5, strategy:2, size:331823
filter:1, level:6, strategy:2, size:331823
filter:1, level:7, strategy:2, size:331823
filter:1, level:8, strategy:2, size:331823
filter:1, level:9, strategy:2, size:331823
filter:3, level:1, strategy:3, size:346952
filter:3, level:2, strategy:3, size:346952
filter:3, level:3, strategy:3, size:346952
filter:3, level:4, strategy:3, size:346952
filter:3, level:5, strategy:3, size:346952
filter:3, level:6, strategy:3, size:346952
filter:3, level:7, strategy:3, size:346952
filter:3, level:8, strategy:3, size:346952
filter:3, level:9, strategy:3, size:346952
filter:2, level:1, strategy:3, size:358276
filter:2, level:2, strategy:3, size:358276
filter:2, level:3, strategy:3, size:358276
filter:2, level:4, strategy:3, size:358276
filter:2, level:5, strategy:3, size:358276
filter:2, level:6, strategy:3, size:358276
filter:2, level:7, strategy:3, size:358276
filter:2, level:8, strategy:3, size:358276
filter:2, level:9, strategy:3, size:358276
filter:3, level:1, strategy:2, size:429431
filter:3, level:2, strategy:2, size:429431
filter:3, level:3, strategy:2, size:429431
filter:3, level:4, strategy:2, size:429431
filter:3, level:5, strategy:2, size:429431
filter:3, level:6, strategy:2, size:429431
filter:3, level:7, strategy:2, size:429431
filter:3, level:8, strategy:2, size:429431
...

---

在压缩PNG时，我不会只依赖ImageMagick（除非有一些超出您自身控制的原因迫使您使用ImageMagick）

将ImageMagick的结果与之进行比较的一个很好的替代方法是，或者是它的一个新的继承者

在优化和压缩方面，这两种方法通常都比ImageMagick获得更好的结果。通常，它们也比IM慢，因为它们可以强制使用不同的方法，然后只保留最小的结果

话虽如此，现在请看ImageMagick

---

使用

convert

定义PNG质量的标准方法是使用

-quality{level}{filter}

参数

但是，通过结合使用

-define png:…

控件，您可以使用更细粒度的控件

-PNG的质量

与JPEG的质量设置非常不同（它只是一个从

0

到

100

的整数）

对于PNG，它由两个单个数字组成：

• 第一个数字（{level}）是（很大程度上）zlib压缩级别，它可以从

  0

  到

  9

  
  （然而，

  0

  的设置有一个特殊的含义：当你使用它时，你会得到哈夫曼压缩，而不是zlib压缩级别0。这通常更好…奇怪但真实。）

• 第二个数字（{filter}）是PNG数据编码过滤器类型（压缩前）：
  • 0表示无
  • 1表示“分包商”
  • 2表示“向上”
  • 3表示“平均”
  • 4表示“Paeth”，以及
  • 5表示“自适应”

在实际操作中会导致：

• 对于带有纯色哈夫曼压缩序列的插图，使用“无”过滤器（

  -quality 00

  ）通常是最合适的
• 对于自然景观的照片，“自适应”过滤（

  -quality 05

  ）通常是最好的

要将其转换为命令行语法，请尝试以下设置：

 -define png:compression-level=0  \
 -define png:compression-filter=5 \ 
 -define png:compression-strategy=2 

---

最后，如果我想真正比较压缩后图像的不同（但接近）清晰度级别，我经常使用Fred Weinstein精彩的脚本

让你妻子测试一下…：-）

---

---

附言：是PNG压缩技术的良好指南。

deflate压缩算法使用65K历史窗口。PNG压缩往往相当缓慢，因为该过程必须将压缩流中的字节序列和窗口中的字节序列进行比较

您可以通过限制窗口的搜索来控制压缩的速度。您可能只搜索一半的缓冲区来查找匹配项，以加快处理过程（因为存在压缩率较低的风险）

在JPEG中，在质量和大小之间进行权衡。在PNG压缩中，在速度和大小之间进行权衡

在任何情况下，PNG压缩过程都是al

identify wallpsw*

 wallpsw.png PNG 1920x1080 1920x1080+0+0 16-bit DirectClass 4.63MB 0.000u 0:00.000
 wallpsw-q95-r1024x768-d8.png[1] PNG 1024x576 1024x576+0+0 8-bit DirectClass 854KB 0.000u 0:00.000

 convert -depth 24 -define png:compression-filter=2 \
         -define png:compression-level=9 -define png:compression-strategy=1

/usr/local/Cellar/imagemagick/7.0.10-61/bin/convert -quality 60% -adaptive-resize 60% input.png output.png

-rwxr-xr-x@ 1 admin  staff   2.4M Jul  3  2020 /Users/admin/Desktop/input.png*
-rw-r--r--  1 admin  staff   781K Feb  7 23:02 /Users/admin/Desktop/output.png