Shows the ordering of pixel data in an integer value

This code has been declared by its author to be Public Domain code.

Shows the ordering of pixel data in an integer value by Zethrax

2012

This is just some code I knocked up to test the ordering of pixel color data in the integer values used with ReadPixel, WritePixel, etc.

If you are using a bank to create or parse the integer color value used with ReadPixel, WritePixel etc, then the bytes that make up the pixel color data are arranged in the following order.

Bank slot:-
Byte 0 = Blue
Byte 1 = Green
Byte 2 = Red
Byte 3 = Alpha

If you are creating or parsing the pixel color data mathmatically then the least significant byte (blue_color_value * 2 ^ 0) holds the color blue. The next higher byte (green_color_value * 2 ^ 8) holds the color green. The next higher byte (red_color_value * 2 ^ 16) holds the color red. The most significant byte (alpha_value * 2 ^ 24) holds the alpha value.

Color byte values range from zero (darkest, or least color) to 255 (lightest, or most color).

The alpha value determines how opaque (visible) the pixel is. An alpha value of zero means that the pixel is invisible. An alpha value of 255 means that the pixel is fully visible. Anything in-between means that the pixel is transparent.

You can also learn more about RGBA color encoding at: http://en.wikipedia.org/wiki/RGBA

Global G_int_bank = CreateBank( 4 )

Graphics 800, 600, 0, 2


image = CreateImage( 64, 64 )
SetBuffer ImageBuffer( image )
For x = 0 To 63
	For y = 0 To 63
		PokeInt G_int_bank, 0, 0 ; Clear the bank.
		PokeByte G_int_bank, 0, 255 ; Store 255 in slot 0.
		WritePixel x, y, PeekInt( G_int_bank, 0 )
	Next
Next 
image1a = image


image = CreateImage( 64, 64 )
SetBuffer ImageBuffer( image )
For x = 0 To 63
	For y = 0 To 63
		PokeInt G_int_bank, 0, 0 ; Clear the bank.
		PokeByte G_int_bank, 1, 255 ; Store 255 in slot 1.
		WritePixel x, y, PeekInt( G_int_bank, 0 )
	Next
Next 
image2a = image


image = CreateImage( 64, 64 )
SetBuffer ImageBuffer( image )
For x = 0 To 63
	For y = 0 To 63
		PokeInt G_int_bank, 0, 0 ; Clear the bank.
		PokeByte G_int_bank, 2, 255 ; Store 255 in slot 2.
		WritePixel x, y, PeekInt( G_int_bank, 0 )
	Next
Next 
image3a = image


image = CreateImage( 64, 64 )
SetBuffer ImageBuffer( image )
For x = 0 To 63
	For y = 0 To 63
		PokeInt G_int_bank, 0, 0 ; Clear the bank.
		PokeByte G_int_bank, 3, 255 ; Store 255 in slot 3.
		WritePixel x, y, PeekInt( G_int_bank, 0 )
	Next
Next 
image4a = image

;---

image = CreateImage( 64, 64 )
SetBuffer ImageBuffer( image )
For x = 0 To 63
	For y = 0 To 63
		WritePixel x, y, 255 ; Set the least significant byte value to 255.
	Next
Next 
image1b = image


image = CreateImage( 64, 64 )
SetBuffer ImageBuffer( image )
For x = 0 To 63
	For y = 0 To 63
		WritePixel x, y, 255 * ( 2 ^ 8 ) ; Set the second byte value to 255.
	Next
Next 
image2b = image


image = CreateImage( 64, 64 )
SetBuffer ImageBuffer( image )
For x = 0 To 63
	For y = 0 To 63
		WritePixel x, y, 255 * ( 2 ^ 16 ) ; Set the third byte value to 255.
	Next
Next 
image3b = image


image = CreateImage( 64, 64 )
SetBuffer ImageBuffer( image )
For x = 0 To 63
	For y = 0 To 63
		WritePixel x, y, 255 * ( 2 ^ 24 ) ; Set the most significant byte value to 255.
	Next
Next 
image4b = image


SetBuffer BackBuffer()

y = o
Text 0, y, "This shows the arrangement of pixel bytes in a bank."
y = y + 20
Text 0, y, "Slot 0 = Blue. Slot 1 = Green. Slot 2 = Red. Slot 3 = Alpha"
y = y + 20
DrawImage image1a, 0, y
DrawImage image2a, 64, y
DrawImage image3a, 128, y
DrawImage image4a, 192, y
y = y + 64 + 20

Text 0, y, "This shows the arrangement of pixel data in an integer value."
y = y + 20
Text 0, y, "Left = Least significant byte (value: 255). Right = Most significant byte (value: 4278190080)."
y = y + 20
DrawImage image1b, 0, y
DrawImage image2b, 64, y
DrawImage image3b, 128, y
DrawImage image4b, 192, y

Flip 

WaitKey
End

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