JPEG: Fix inverted handling of GDAL_ERROR_ON_LIBJPEG_WARNING

[kevinmehall]

What does this PR do?

Since #7016, the behavior of the GDAL_ERROR_ON_LIBJPEG_WARNING option is inverted, producing errors when FALSE and warnings when TRUE for the types of problems that are warnings by default. For example:

$ gdal_translate byte_corrupted3.jpg out.png
Warning 1: libjpeg: Corrupt JPEG data: 20 extraneous bytes before marker 0xda (this warning
can be turned as an error by setting GDAL_ERROR_ON_LIBJPEG_WARNING to TRUE)
Input file size is 24, 24
0...10...20...30...40...50...60...70...80...90...100 - done.

$ GDAL_ERROR_ON_LIBJPEG_WARNING=TRUE gdal_translate byte_corrupted3.jpg out.png
Warning 1: libjpeg: Corrupt JPEG data: 20 extraneous bytes before marker 0xda
Input file size is 24, 24
0...10...20...30...40...50...60...70...80...90...100 - done.

$ GDAL_ERROR_ON_LIBJPEG_WARNING=FALSE gdal_translate byte_corrupted3.jpg out.png
ERROR 1: libjpeg: Corrupt JPEG data: 20 extraneous bytes before marker 0xda
Input file size is 24, 24
ERROR 1: byte_corrupted3.jpg, band 1: IReadBlock failed at X offset 0, Y offset 0
ERROR 1: libpng: No IDATs written into file

The byte_corrupted3.jpg file was generated with:

from osgeo import gdal

src_ds = gdal.GetDriverByName("Mem").Create("", 24, 24)
src_ds.GetRasterBand(1).Fill(0xff)
ds = gdal.GetDriverByName("JPEG").CreateCopy("/vsimem/x.jpg", src_ds)
vsifile = gdal.VSIFOpenL("/vsimem/x.jpg", 'r')
b = list(gdal.VSIFReadL(1, 1024, vsifile))

b[0x93:0x93] = [0] * 20

open('autotest/gdrivers/data/jpeg/byte_corrupted3.jpg', 'wb').write(bytes(b))

Tasklist

• Make sure code is correctly formatted (cf pre-commit configuration)
• Add test case(s)
• Add documentation
• Updated Python API documentation (swig/include/python/docs/)
• Review
• Adjust for comments
• All CI builds and checks have passed

[coveralls]

coverage: 69.362%. remained the same
when pulling 29b0bad on kevinmehall:jpeg-warning
into acca3c2 on OSGeo:master.

[rouault]

Thanks!