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path: root/src/ipa/simple/black_level.h
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2024-06-02libcamera: software_isp: Use a specific integer type for black levelMilan Zamazal
The documented range of values corresponds to uint8_t, so let's use that type. Signed-off-by: Milan Zamazal <mzamazal@redhat.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Andrei Konovalov <andrey.konovalov.ynk@gmail.com> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
2024-05-08libcamera: Drop file name from header comment blocksLaurent Pinchart
Source files in libcamera start by a comment block header, which includes the file name and a one-line description of the file contents. While the latter is useful to get a quick overview of the file contents at a glance, the former is mostly a source of inconvenience. The name in the comments can easily get out of sync with the file name when files are renamed, and copy & paste during development have often lead to incorrect names being used to start with. Readers of the source code are expected to know which file they're looking it. Drop the file name from the header comment block. The change was generated with the following script: ---------------------------------------- dirs="include/libcamera src test utils" declare -rA patterns=( ['c']=' \* ' ['cpp']=' \* ' ['h']=' \* ' ['py']='# ' ['sh']='# ' ) for ext in ${!patterns[@]} ; do files=$(for dir in $dirs ; do find $dir -name "*.${ext}" ; done) pattern=${patterns[${ext}]} for file in $files ; do name=$(basename ${file}) sed -i "s/^\(${pattern}\)${name} - /\1/" "$file" done done ---------------------------------------- This misses several files that are out of sync with the comment block header. Those will be addressed separately and manually. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
2024-04-16libcamera: software_isp: Apply black level compensationMilan Zamazal
Black may not be represented as 0 pixel value for given hardware, it may be higher. If this is not compensated then various problems may occur such as low contrast or suboptimal exposure. The black pixel value can be either retrieved from a tuning file for the given hardware, or automatically on the fly. The former is the right and correct method, while the latter can be used when a tuning file is not available for the given hardware. Since there is currently no support for tuning files in software ISP, the automatic, hardware independent way, is always used. Support for tuning files should be added in future but it will require more work than this patch. The patch looks at the image histogram and assumes that black starts when pixel values start occurring on the left. A certain amount of the darkest pixels is ignored; it doesn't matter whether they represent various kinds of noise or are real, they are better to omit in any case to make the image looking better. It also doesn't matter whether the darkest pixels occur around the supposed black level or are spread between 0 and the black level, the difference is not important. An arbitrary threshold of 2% darkest pixels is applied; there is no magic about that value. The patch assumes that the black values for different colors are the same and doesn't attempt any other non-primitive enhancements. It cannot completely replace tuning files and simplicity, while providing visible benefit, is its goal. Anything more sophisticated is left for future patches. A possible cheap enhancement, if needed, could be setting exposure + gain to minimum values temporarily, before setting the black level. In theory, the black level should be fixed but it may not be reached in all images. For this reason, the patch updates black level only if the observed value is lower than the current one; it should be never increased. The purpose of the patch is to compensate for hardware properties. General image contrast enhancements are out of scope of this patch. Stats are still gathered as an uncorrected histogram, to avoid any confusion and to represent the raw image data. Exposure must be determined after the black level correction -- it has no influence on the sub-black area and must be correct after applying the black level correction. The granularity of the histogram is increased from 16 to 64 to provide a better precision (there is no theory behind either of those numbers). Reviewed-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Milan Zamazal <mzamazal@redhat.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Milan Zamazal <mzamazal@redhat.com> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>