How to trigger:
See Dialog.png for the feature triggering the bug.
The bug is active after enabling he feature and restarting Irfanview. The current session is not affected.
To deactivate the bug, you must disable the feature and restart Irfanview again.
What happens?
All IrfanView operations are particulary damaging to dark areas of images.
Normal lossless operations become lossy.
All means:
Test image
Grey.ASCII.pgm:
------------------------------------------------------------------
P2
# Created by Frank Klemm
16 16
255
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255
------------------------------------------------------------------
or take attached Grey-Org.png
When you load the image and save it without any processing, the file looks like this:
------------------------------------------------------------------
P2
# Damaged by IrfanView
16 16
255
0 0 0 0 6 6 6 6 9 9 9 12 12 12 15 15 15 18 18 20 20 20 22 22 24 24 26 26 28 28 30 30 32 34 34 35 35 37 39 39 40 40 42 44 44 45 47 47 48 50 50 51 53 53 54 55 55 57 58 60 60 61 62 63 63 65 66 67 69 69 70 71 72 74 74 75 76 77 78 80 80 81 82 83 84 85 86 86 88 89 90 91 92 93 94 95 96 97 97 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255
------------------------------------------------------------------
i.e. pixel values are recoded
0...3 => 0
4...7 => 6
8...10 => 9
11...13 => 12
13...16 => 15
17, 18 => 18
...
33, 34 => 34
...
largest effected pixel value is 98 which is recoded as 97.
Severity of the Bug
Not obvious damaging pictures in all lossless operations.
This is one of the worst kind of bugs ...
Remark
Actually there are multiple issues.
1. Resampling using "Try to improve gamma for Resample" works very poorly.
2. Settings of the Resampling dialog are effecting the display of Irfanview.
3. Settings of the Resampling dialog are effecting ALL lossless operations.
Not to mention that "Try to improve the gamma for resampling" actually means "use linear color space for resampling".
No excuses are ...
See Dialog.png for the feature triggering the bug.
The bug is active after enabling he feature and restarting Irfanview. The current session is not affected.
To deactivate the bug, you must disable the feature and restart Irfanview again.
What happens?
All IrfanView operations are particulary damaging to dark areas of images.
Normal lossless operations become lossy.
All means:
- Resampling
- Display of images independent of resampling (i.e. also 100%)
- Simple file operations like converting file formats, cropping, flipping, changing canvas size, ...
Test image
Grey.ASCII.pgm:
------------------------------------------------------------------
P2
# Created by Frank Klemm
16 16
255
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255
------------------------------------------------------------------
or take attached Grey-Org.png
When you load the image and save it without any processing, the file looks like this:
------------------------------------------------------------------
P2
# Damaged by IrfanView
16 16
255
0 0 0 0 6 6 6 6 9 9 9 12 12 12 15 15 15 18 18 20 20 20 22 22 24 24 26 26 28 28 30 30 32 34 34 35 35 37 39 39 40 40 42 44 44 45 47 47 48 50 50 51 53 53 54 55 55 57 58 60 60 61 62 63 63 65 66 67 69 69 70 71 72 74 74 75 76 77 78 80 80 81 82 83 84 85 86 86 88 89 90 91 92 93 94 95 96 97 97 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255
------------------------------------------------------------------
i.e. pixel values are recoded
0...3 => 0
4...7 => 6
8...10 => 9
11...13 => 12
13...16 => 15
17, 18 => 18
...
33, 34 => 34
...
largest effected pixel value is 98 which is recoded as 97.
Severity of the Bug
Not obvious damaging pictures in all lossless operations.
This is one of the worst kind of bugs ...
Remark
Actually there are multiple issues.
1. Resampling using "Try to improve gamma for Resample" works very poorly.
2. Settings of the Resampling dialog are effecting the display of Irfanview.
3. Settings of the Resampling dialog are effecting ALL lossless operations.
Not to mention that "Try to improve the gamma for resampling" actually means "use linear color space for resampling".
No excuses are ...
- This feature is not activated by default.
- It's been like that forever.
- Nobody has complained so far.
- The program is free for private use.
- You can use other programs.
- You can disable this feature.
- ... and other hundred excuses I programmers normally use every day.
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