Take decode arrays into account when processing grayscale images #159
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Reviewable status: 0 of 3 files reviewed, 1 unresolved discussion (waiting on @adrg)
model/image.go, line 92 at r1 (raw file):
data := img.Data lenData := len(img.Data) maxVal := math.Pow(2, float64(img.BitsPerComponent)) - 1
How about changing the math.Pow with (uint32(1) << img.BitsPerComponent) - 1? The arithmetic shift is one of the processors instructions, and it is a good practice to use it for operations that gets the powers of 2.
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Reviewable status: 0 of 4 files reviewed, 1 unresolved discussion (waiting on @kucjac)
model/image.go, line 92 at r1 (raw file):
Previously, kucjac (Jacek Kucharczyk) wrote…
How about changing the
math.Powwith(uint32(1) << img.BitsPerComponent) - 1? The arithmetic shift is one of the processors instructions, and it is a good practice to use it for operations that gets the powers of2.
Done.
Some of the image extraction test case files contain custom decode arrays for grayscale images.
The default decode array for grayscale images is [0.0 1.0] which means that 0.0 is black and 1.0 is white. Some of the files had reversed decode arrays [1.0 0.0] which basically means that 0.0 is white and 1.0 is black. As a result, the images in cause were not exported as they are in the test PDF files.
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