8 | | === Will increasing RAM increase the speed of gdalwarp? === |
| 8 | == What if '''nodata''' is different in each image? == |
| 9 | |
| 10 | If the ''nodata'' tag is set in the geotiff header, gdalwarp will use it automatically, you don't need to do anything. However, `-srcnodata` overrides this, so if you are handling a bunch of images with different values to be ignored you need to either a) pre-process them to have the same to-be-ignored value, or b) set the nodata flag for each file. Use (b) if you need to preserve the original values for some reason, for example: |
| 11 | |
| 12 | {{{ |
| 13 | # for this image we want to ignore black (0) |
| 14 | gdalwarp -srcnodata 0 -dstnodata 0 orig-ignore-black.tif black-nodata.tif |
| 15 | |
| 16 | # and now we want to ignore white (0) |
| 17 | gdalwarp -srcnodata 255 -dstnodata 255 orig-ignore-white.tif white-nodata.tif |
| 18 | |
| 19 | # and finally ignore a particular blue-grey (RGB 125 125 150) |
| 20 | gdalwarp -srcnodata "125 125 150" -dstnodata "125 125 150" orig-ignore-grey.tif grey-nodata.tif |
| 21 | |
| 22 | # now we can mosaic them all and not worry about nodata parameters |
| 23 | gdalwarp black-nodata.tif grey-nodata.tif white-nodata.tif final-mosaic.tif |
| 24 | }}} |
| 25 | |
| 26 | |
| 27 | |
| 28 | == Will increasing RAM increase the speed of gdalwarp? == |