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<div class="">Hi,</div>
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<div class="">I need to convert 524 288 color png tiles to black and white png.</div>
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<div class="">=> The lands always have the 2 colors RGB (RGBA?) 59,89,95,255 and / or 60,89,96,255.</div>
<div class="">=> The sea always has the colors RGB 109,178,200,255 / 138,193,212,255 and 161,205,220,255.</div>
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<div class="">Some tiles contain only land, others only sea and still others contain land and at least 1 color of the sea ...</div>
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<div class="">I use gdal_translate to georeference and assign a projection to each tile (via script) with the following command (and it works perfectly):</div>
<div class=""><i class="">gdal_translate -a_srs EPSG: 4326 -a_ullr <ulx> <uly> <lrx> <lry> input.png output.tiff</i></div>
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<div class="">I have read and reread, in every way, the gdal_translate help with the args
<i class="">-b</i> and <i class="">-mask</i> and I don't understand how to use it ...</div>
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<div class="">I need all the sea colors to always be Black and all the lands colors to be White.</div>
<div class="">(I polygonize each tile afterwards)</div>
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<div class="">How can I do this via gdal_translate or other gdal program?</div>
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<div class="">Thanks for your help</div>
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<div class="">PS:</div>
<div class="">What gdalinfo gives me for a random tile (original png)</div>
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<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">gdalinfo map_11_0_309.png </span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Driver: PNG/Portable Network Graphics</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Files: map_11_0_309.png</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Size is 256, 256</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Coordinate System is `'</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Corner Coordinates:</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Upper Left ( 0.0, 0.0)</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Lower Left ( 0.0, 256.0)</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Upper Right ( 256.0, 0.0)</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Lower Right ( 256.0, 256.0)</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Center ( 128.0, 128.0)</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">Band 1 Block=256x1 Type=Byte, ColorInterp=Palette</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class=""> Image Structure Metadata:</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class=""> NBITS=2</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class=""> Color Table (RGB with 4 entries)</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class=""> 0: 60,89,96,255</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class=""> 1: 109,178,200,255</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class=""> 2: 138,193,212,255</span></div>
<div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Monaco; color: rgb(16, 16, 16); background-color: rgba(255, 255, 255, 0.85098);" class="">
<span style="font-variant-ligatures: no-common-ligatures" class=""> 3: 161,205,220,255</span></div>
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