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Get the overall brightness level of a picture?
Posted: Mon May 06, 2019 7:49 pm
by forumuser
Hi,
is it possible to load e.g. a .jpg file and analyze it for the level of brightness?
The picture should NOT be displayed!
Reason: I have thousands of pictures that were taken with very! low light and
are 95% just... black.
I'd like to identify those without human interaction
Re: Get the overall brightness level of a picture?
Posted: Mon May 06, 2019 8:58 pm
by Mijikai
Read every 2nd pixel and compare it its grayscale value to a defined thereshold.
Get the number (%) of pixels that passed.
Re: Get the overall brightness level of a picture?
Posted: Mon May 06, 2019 9:13 pm
by Sicro
Code: Select all
UseJPEGImageDecoder()
UseJPEG2000ImageDecoder()
UsePNGImageDecoder()
UseTIFFImageDecoder()
UseTGAImageDecoder()
UseGIFImageDecoder()
Procedure.d GetBrightnessOfColor(color)
; http://fseitz.de/blog/index.php?/archives/112-Helligkeit-von-Farben-des-RGB-Farbraums-berechnen.html
ProcedureReturn Sqr(0.299 * Pow(Red(color), 2) + 0.587 * Pow(Green(color), 2) + 0.114 * Pow(Blue(color), 2))
EndProcedure
Define.d totalImageBrightness, averageBrightness
Define x, y, countOfAllfPixels, pixelColor
Define imageFilePath$
imageFilePath$ = OpenFileRequester("Open image file", "", "", 0)
image = LoadImage(#PB_Any, imageFilePath$)
If Not image
Debug "Error"
End
EndIf
countOfAllfPixels = ImageWidth(image) * ImageHeight(image)
If Not StartDrawing(ImageOutput(image))
Debug "Error"
End
EndIf
For x = ImageWidth(image) - 1 To 0 Step -1
For y = ImageHeight(image) - 1 To 0 Step -1
pixelColor = Point(x, y)
totalImageBrightness + GetBrightnessOfColor(pixelColor)
Next
Next
StopDrawing()
FreeImage(image)
averageBrightness = totalImageBrightness / countOfAllfPixels
Debug averageBrightness
Re: Get the overall brightness level of a picture?
Posted: Mon May 06, 2019 10:35 pm
by forumuser
@Mijikai
Thanks for the hint!
@Sicro
Holy cow, that's amazing!
I've changed the step value to -4 to make it faster
and the matching quote for the dark pictures is ~99%
Re: Get the overall brightness level of a picture?
Posted: Tue May 07, 2019 7:41 am
by Michael Vogel
I've used a CustomFilter from time to time in similar cases to speed up things...
...but keep in mind to use a global variable for summarizing the pixel info within the callback routine.
Code: Select all
UseJPEGImageDecoder()
UseJPEG2000ImageDecoder()
UsePNGImageDecoder()
UseTIFFImageDecoder()
UseTGAImageDecoder()
Define x, y, countOfAllfPixels, pixelColor
Define imageFilePath$
Global TotalImageBrightness.d
Procedure Brightness(x,y,c,d)
x=c&$FF
y=(c>>8)&$FF
c=(c>>16)&$FF
TotalImageBrightness+Sqr(x*x*0.299+y*y*0.587+c*c*0.114)
EndProcedure
imageFilePath$= "IQ.png"
If FileSize(imageFilePath$)<0
imageFilePath$= OpenFileRequester("Open image file", "", "", 0)
EndIf
If FileSize(imageFilePath$)>0
image = LoadImage(#PB_Any, imageFilePath$)
If image>=0
countOfAllfPixels = ImageWidth(image) * ImageHeight(image)
TotalImageBrightness=0
StartDrawing(ImageOutput(image))
CustomFilterCallback(@Brightness())
DrawingMode(#PB_2DDrawing_CustomFilter)
DrawImage(ImageID(image),0,0)
StopDrawing()
FreeImage(image)
Debug totalImageBrightness / countOfAllfPixels
EndIf
EndIf
Re: Get the overall brightness level of a picture?
Posted: Sat Nov 19, 2022 9:41 pm
by novablue
I would like do dim down every picture to the same rough brightness level to use it as a background.
Could someone smart modify this code to also SET the overall brightness of a picture?
