Legacy ImageMagick Discussions Archive

Hi,

Here is the GIF:

The identify command-line tool reports that each frame has such transparent color:

Transparent color: none

I used the following command:

Code: Select all

identify -verbose  cat.gif | grep -C 1 Transparent

I also tried to use this command (it was suggested here):

Code: Select all

convert cat.gif -coalesce -channel a -separate -scale 1x1! -format "%[fx:u]\n" info:

And it also reports that each GIF frame is non-transparent.

However, checking this GIF with gifsicle and verifying the appropriate bytes with a hex editor clearly shows that the frames have transparent colors:

Code: Select all

  + image #0 320x203 transparent 117
    disposal asis delay 0.30s
  + image #1 320x203 transparent 116
    local color table [128]
    disposal asis delay 0.20s
  + image #2 320x203 transparent 112
    local color table [128]
    disposal asis delay 0.10s
  + image #3 320x203 transparent 114
    local color table [128]
    disposal asis delay 0.10s
  + image #4 320x203 transparent 108
    local color table [128]
    disposal asis delay 0.10s
  + image #5 320x203 transparent 109
    local color table [128]
    disposal asis delay 0.10s
  + image #6 320x203 transparent 103
    local color table [128]
    disposal asis delay 0.10s
  + image #7 320x203 transparent 109
    local color table [128]
    disposal asis delay 0.10s
  + image #8 320x203 transparent 108
    local color table [128]
    disposal asis delay 0.10s
  + image #9 320x203 transparent 108
    local color table [128]
    disposal asis delay 0.10s
  + image #10 320x203 transparent 108
    local color table [128]
    disposal asis delay 0.10s
  + image #11 320x203 transparent 110
    local color table [128]
    disposal asis delay 0.10s
  + image #12 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #13 320x203 transparent 107
    local color table [128]
    disposal asis delay 0.10s
  + image #14 320x203 transparent 108
    local color table [128]
    disposal asis delay 0.10s
  + image #15 320x203 transparent 109
    local color table [128]
    disposal asis delay 0.10s
  + image #16 320x203 transparent 109
    local color table [128]
    disposal asis delay 0.10s
  + image #17 320x203 transparent 107
    local color table [128]
    disposal asis delay 0.10s
  + image #18 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #19 320x203 transparent 109
    local color table [128]
    disposal asis delay 0.10s
  + image #20 320x203 transparent 111
    local color table [128]
    disposal asis delay 0.10s
  + image #21 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #22 320x203 transparent 111
    local color table [128]
    disposal asis delay 0.10s
  + image #23 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #24 320x203 transparent 105
    local color table [128]
    disposal asis delay 0.10s
  + image #25 320x203 transparent 108
    local color table [128]
    disposal asis delay 0.10s
  + image #26 320x203 transparent 104
    local color table [128]
    disposal asis delay 0.10s
  + image #27 320x203 transparent 104
    local color table [128]
    disposal asis delay 0.10s
  + image #28 320x203 transparent 104
    local color table [128]
    disposal asis delay 0.10s
  + image #29 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #30 320x203 transparent 107
    local color table [128]
    disposal asis delay 0.10s
  + image #31 320x203 transparent 104
    local color table [128]
    disposal asis delay 0.10s
  + image #32 320x203 transparent 97
    local color table [128]
    disposal asis delay 0.10s
  + image #33 320x203 transparent 101
    local color table [128]
    disposal asis delay 0.10s
  + image #34 320x203 transparent 98
    local color table [128]
    disposal asis delay 0.10s
  + image #35 320x203 transparent 98
    local color table [128]
    disposal asis delay 0.10s
  + image #36 320x203 transparent 94
    local color table [128]
    disposal asis delay 0.10s
  + image #37 320x203 transparent 96
    local color table [128]
    disposal asis delay 0.10s
  + image #38 320x203 transparent 96
    local color table [128]
    disposal asis delay 0.10s
  + image #39 320x203 transparent 95
    local color table [128]
    disposal asis delay 0.10s
  + image #40 320x203 transparent 94
    local color table [128]
    disposal asis delay 0.10s
  + image #41 320x203 transparent 94
    local color table [128]
    disposal asis delay 0.10s
  + image #42 320x203 transparent 93
    local color table [128]
    disposal asis delay 0.10s
  + image #43 320x203 transparent 95
    local color table [128]
    disposal asis delay 0.10s
  + image #44 320x203 transparent 97
    local color table [128]
    disposal asis delay 0.10s
  + image #45 320x203 transparent 101
    local color table [128]
    disposal asis delay 0.10s
  + image #46 320x203 transparent 99
    local color table [128]
    disposal asis delay 0.10s
  + image #47 320x203 transparent 97
    local color table [128]
    disposal asis delay 0.10s
  + image #48 320x203 transparent 90
    local color table [128]
    disposal asis delay 0.10s
  + image #49 320x203 transparent 87
    local color table [128]
    disposal asis delay 0.10s
  + image #50 320x203 transparent 91
    local color table [128]
    disposal asis delay 0.10s
  + image #51 320x203 transparent 95
    local color table [128]
    disposal asis delay 0.10s
  + image #52 320x203 transparent 95
    local color table [128]
    disposal asis delay 0.10s
  + image #53 320x203 transparent 96
    local color table [128]
    disposal asis delay 0.10s
  + image #54 320x203 transparent 93
    local color table [128]
    disposal asis delay 0.10s
  + image #55 320x203 transparent 91
    local color table [128]
    disposal asis delay 0.10s
  + image #56 320x203 transparent 102
    local color table [128]
    disposal asis delay 0.10s
  + image #57 320x203 transparent 99
    local color table [128]
    disposal asis delay 0.10s
  + image #58 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #59 320x203 transparent 107
    local color table [128]
    disposal asis delay 0.10s
  + image #60 320x203 transparent 113
    local color table [128]
    disposal asis delay 0.10s
  + image #61 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #62 320x203 transparent 107
    local color table [128]
    disposal asis delay 0.10s
  + image #63 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #64 320x203 transparent 107
    local color table [128]
    disposal asis delay 0.10s
  + image #65 320x203 transparent 108
    local color table [128]
    disposal asis delay 0.10s
  + image #66 320x203 transparent 107
    local color table [128]
    disposal asis delay 0.10s
  + image #67 320x203 transparent 104
    local color table [128]
    disposal asis delay 0.10s
  + image #68 320x203 transparent 104
    local color table [128]
    disposal asis delay 0.10s
  + image #69 320x203 transparent 104
    local color table [128]
    disposal asis delay 0.10s
  + image #70 320x203 transparent 107
    local color table [128]
    disposal asis delay 0.10s
  + image #71 320x203 transparent 105
    local color table [128]
    disposal asis delay 0.10s
  + image #72 320x203 transparent 101
    local color table [128]
    disposal asis delay 0.10s
  + image #73 320x203 transparent 101
    local color table [128]
    disposal asis delay 0.10s
  + image #74 320x203 transparent 103
    local color table [128]
    disposal asis delay 0.10s
  + image #75 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #76 320x203 transparent 103
    local color table [128]
    disposal asis delay 0.10s
  + image #77 320x203 transparent 103
    local color table [128]
    disposal asis delay 0.10s
  + image #78 320x203 transparent 97
    local color table [128]
    disposal asis delay 0.10s
  + image #79 320x203 transparent 102
    local color table [128]
    disposal asis delay 0.10s
  + image #80 320x203 transparent 99
    local color table [128]
    disposal asis delay 0.10s
  + image #81 320x203 transparent 104
    local color table [128]
    disposal asis delay 0.10s
  + image #82 320x203 transparent 104
    local color table [128]
    disposal asis delay 0.10s
  + image #83 320x203 transparent 103
    local color table [128]
    disposal asis delay 0.10s
  + image #84 320x203 transparent 105
    local color table [128]
    disposal asis delay 0.10s
  + image #85 320x203 transparent 101
    local color table [128]
    disposal asis delay 0.10s
  + image #86 320x203 transparent 104
    local color table [128]
    disposal asis delay 0.10s
  + image #87 320x203 transparent 102
    local color table [128]
    disposal asis delay 0.10s
  + image #88 320x203 transparent 100
    local color table [128]
    disposal asis delay 0.10s
  + image #89 320x203 transparent 103
    local color table [128]
    disposal asis delay 0.10s
  + image #90 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #91 320x203 transparent 105
    local color table [128]
    disposal asis delay 0.10s
  + image #92 320x203 transparent 105
    local color table [128]
    disposal asis delay 0.10s
  + image #93 320x203 transparent 103
    local color table [128]
    disposal asis delay 0.10s
  + image #94 320x203 transparent 101
    local color table [128]
    disposal asis delay 0.10s
  + image #95 320x203 transparent 98
    local color table [128]
    disposal asis delay 0.10s
  + image #96 320x203 transparent 100
    local color table [128]
    disposal asis delay 0.10s
  + image #97 320x203 transparent 99
    local color table [128]
    disposal asis delay 0.10s
  + image #98 320x203 transparent 102
    local color table [128]
    disposal asis delay 0.10s
  + image #99 320x203 transparent 103
    local color table [128]
    disposal asis delay 0.10s
  + image #100 320x203 transparent 100
    local color table [128]
    disposal asis delay 0.10s
  + image #101 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #102 320x203 transparent 102
    local color table [128]
    disposal asis delay 0.10s
  + image #103 320x203 transparent 102
    local color table [128]
    disposal asis delay 0.10s
  + image #104 320x203 transparent 105
    local color table [128]
    disposal asis delay 0.10s
  + image #105 320x203 transparent 110
    local color table [128]
    disposal asis delay 0.10s
  + image #106 320x203 transparent 105
    local color table [128]
    disposal asis delay 0.10s
  + image #107 320x203 transparent 108
    local color table [128]
    disposal asis delay 0.10s
  + image #108 320x203 transparent 100
    local color table [128]
    disposal asis delay 0.10s
  + image #109 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #110 320x203 transparent 106
    local color table [128]
    disposal asis delay 0.10s
  + image #111 320x203 transparent 103
    local color table [128]
    disposal asis delay 0.10s
  + image #112 320x203 transparent 101
    local color table [128]
    disposal asis delay 0.10s
  + image #113 320x203 transparent 105
    local color table [128]
    disposal asis delay 0.10s
  + image #114 320x203 transparent 94
    local color table [128]
    disposal asis delay 0.10s
  + image #115 320x203 transparent 97
    local color table [128]
    disposal asis delay 0.10s
  + image #116 320x203 transparent 100
    local color table [128]
    disposal asis delay 0.10s
  + image #117 320x203 transparent 96
    local color table [128]
    disposal asis delay 0.10s
  + image #118 320x203 transparent 90
    local color table [128]
    disposal asis delay 0.10s
  + image #119 320x203 transparent 87
    local color table [128]
    disposal asis delay 0.10s
  + image #120 320x203 transparent 97
    local color table [128]
    disposal asis delay 0.10s
  + image #121 320x203 transparent 96
    local color table [128]
    disposal asis delay 0.10s
  + image #122 320x203 transparent 95
    local color table [128]
    disposal asis delay 0.10s
  + image #123 320x203 transparent 94
    local color table [128]
    disposal asis delay 0.10s
  + image #124 320x203 transparent 99
    local color table [128]
    disposal asis delay 0.10s
  + image #125 320x203 transparent 97
    local color table [128]
    disposal asis delay 0.10s
  + image #126 320x203 transparent 96
    local color table [128]
    disposal asis delay 0.10s
  + image #127 320x203 transparent 98
    local color table [128]
    disposal asis delay 0.10s
  + image #128 320x203 transparent 99
    local color table [128]
    disposal asis delay 0.10s
  + image #129 320x203 transparent 95
    local color table [128]
    disposal asis delay 0.10s
  + image #130 320x203 transparent 97
    local color table [128]
    disposal asis delay 0.10s
  + image #131 320x203 transparent 102
    local color table [128]
    disposal asis delay 0.10s
  + image #132 320x203 transparent 94
    local color table [128]
    disposal asis delay 0.10s
  + image #133 320x203 transparent 93
    local color table [128]
    disposal asis delay 0.10s
  + image #134 320x203 transparent 94
    local color table [128]
    disposal asis delay 0.10s
  + image #135 320x203 transparent 95
    local color table [128]
    disposal asis delay 0.10s
  + image #136 320x203 transparent 97
    local color table [128]
    disposal asis delay 0.10s
  + image #137 320x203 transparent 96
    local color table [128]
    disposal asis delay 0.10s
  + image #138 320x203 transparent 92
    local color table [128]
    disposal asis delay 0.10s
  + image #139 320x203 transparent 94
    local color table [128]
    disposal asis delay 0.10s
  + image #140 320x203 transparent 93
    local color table [128]
    disposal asis delay 0.10s
  + image #141 320x203 transparent 96
    local color table [128]
    disposal asis delay 0.10s
  + image #142 320x203 transparent 95
    local color table [128]
    disposal asis delay 0.10s
  + image #143 320x203 transparent 97
    local color table [128]
    disposal asis delay 0.10s
  + image #144 320x203 transparent 93
    local color table [128]
    disposal asis delay 0.10s
  + image #145 320x203 transparent 93
    local color table [128]
    disposal asis delay 0.10s
  + image #146 320x203 transparent 94
    local color table [128]
    disposal asis delay 0.10s
  + image #147 320x203 transparent 98
    local color table [128]
    disposal asis delay 0.10s
  + image #148 320x203 transparent 93
    local color table [128]
    disposal asis delay 0.10s
  + image #149 320x203 transparent 95
    local color table [128]
    disposal asis delay 0.10s
  + image #150 320x203 transparent 100
    local color table [128]
    disposal asis delay 0.10s
  + image #151 320x203 transparent 100
    local color table [128]
    disposal asis delay 0.10s
  + image #152 320x203 transparent 100
    local color table [128]
    disposal asis delay 0.10s
  + image #153 320x203 transparent 99
    local color table [128]
    disposal asis delay 0.10s
  + image #154 320x203 transparent 98
    local color table [128]
    disposal asis delay 0.10s
  + image #155 320x203 transparent 99
    local color table [128]
    disposal asis delay 0.10s
  + image #156 320x203 transparent 96
    local color table [128]
    disposal asis delay 0.10s
  + image #157 320x203 transparent 101
    local color table [128]
    disposal asis delay 0.10s
  + image #158 320x203 transparent 109
    local color table [128]
    disposal asis delay 0.10s
  + image #159 320x203 transparent 119
    local color table [128]
    disposal asis delay 0.10s
  + image #160 320x203 transparent 119
    local color table [128]
    disposal asis delay 0.10s
  + image #161 320x203 transparent 125
    local color table [128]
    disposal asis delay 0.10s
  + image #162 320x203 transparent 119
    local color table [128]
    disposal asis delay 0.10s
  + image #163 320x203 transparent 122
    local color table [128]
    disposal asis delay 0.10s
  + image #164 320x203 transparent 120
    local color table [128]
    disposal asis delay 0.10s
  + image #165 320x203 transparent 123
    local color table [128]
    disposal asis delay 0.10s
  + image #166 320x203 transparent 125
    local color table [128]
    disposal asis delay 0.10s
  + image #167 320x203 transparent 122
    local color table [128]
    disposal asis delay 0.10s
  + image #168 320x203 transparent 122
    local color table [128]
    disposal asis delay 0.10s
  + image #169 320x203 transparent 123
    local color table [128]
    disposal asis delay 0.10s
  + image #170 320x203 transparent 121
    local color table [128]
    disposal asis delay 0.10s
  + image #171 320x203 transparent 121
    local color table [128]
    disposal asis delay 0.10s
  + image #172 320x203 transparent 118
    local color table [128]
    disposal asis delay 0.10s
  + image #173 320x203 transparent 116
    local color table [128]
    disposal asis delay 0.10s
  + image #174 320x203 transparent 112
    local color table [128]
    disposal asis delay 0.10s
  + image #175 320x203 transparent 119
    local color table [128]
    disposal asis delay 0.10s
  + image #176 320x203 transparent 119
    local color table [128]
    disposal asis delay 0.10s
  + image #177 320x203 transparent 120
    local color table [128]
    disposal asis delay 0.10s
  + image #178 320x203 transparent 121
    local color table [128]
    disposal asis delay 0.10s
  + image #179 320x203 transparent 117
    local color table [128]
    disposal asis delay 0.10s
  + image #180 320x203 transparent 115
    local color table [128]
    disposal asis delay 0.10s
  + image #181 320x203 transparent 114
    local color table [128]
    disposal asis delay 0.10s
  + image #182 320x203 transparent 116
    local color table [128]
    disposal asis delay 0.10s
  + image #183 320x203 transparent 117
    local color table [128]
    disposal asis delay 0.10s
  + image #184 320x203 transparent 116
    local color table [128]
    disposal asis delay 0.10s
  + image #185 320x203 transparent 114
    local color table [128]
    disposal asis delay 0.10s
  + image #186 320x203 transparent 111
    local color table [128]
    disposal asis delay 0.10s
  + image #187 320x203 transparent 110
    local color table [128]
    disposal asis delay 0.10s
  + image #188 320x203 transparent 110
    local color table [128]
    disposal asis delay 0.10s
  + image #189 320x203 transparent 111
    local color table [128]
    disposal asis delay 0.10s
  + image #190 320x203 transparent 111
    local color table [128]
    disposal asis delay 0.10s
  + image #191 320x203 transparent 113
    local color table [128]
    disposal asis delay 0.10s
  + image #192 320x203 transparent 107
    local color table [128]
    disposal asis delay 0.20s
  + image #193 320x203 transparent 109
    local color table [128]
    disposal asis delay 0.30s
  + image #194 320x203 transparent 109
    local color table [128]
    disposal asis delay 0.40s

Just in case, here is the gifsicle command:

Code: Select all

gifsicle -II cat.gif

So I'm wondering is this a bug or ImageMagick just uses some clever algorithm to detect whether the transparent color is really used in a GIF frame? I'm actually looking for such algorithm

Thanks.

Not every frame has transparent color of none. Your first frame reports Transparent color: srgba(171,172,173,0).

Sorry but I am not really sure what you are asking?

Please always provide your IM version and platform.

I'm sorry if my question wasn't clear enough. I'll ask it again.

IM Version: ImageMagick 7.0.5-4 Q16 x86_64 2017-03-25
Platform: macOS Sierra 10.12.3

Why identify utility reports for all (except the first one) GIF frames Transparent color: none? It seems that this is incorrect because:

1. gifsicle reports different transparent color values
2. the values reported by gifsicle were verified using the hex editor.

Legacy ImageMagick Discussions Archive

Possibly wrong report regarding GIF transparency

Possibly wrong report regarding GIF transparency

Re: Possibly wrong report regarding GIF transparency

Re: Possibly wrong report regarding GIF transparency