Point

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Point

Returns the colour of a pixel, or -1 if it is off the screen or image.

Syntax

result = Point( coord_x, coord_y [,buffer] )
result = Point( function_index )

Description

GfxLib Function with two different uses.
If supplied with two coordinates it reads the color of the pixel at the coordinate coord_x, coord_y of the screen, or of the buffer, if supplied.
The value return is a color index in a 256 or less color Screen (Graphics), and an RGB value in true color modes. If the coordinates are off-screen or off-buffer, -1 is returned

If supplied with a single value it returns the one of the coordinates of the graphics cursor as set by the last graphics command executed. If the last command was executed in a buffer, the values returned will be coordinates in the buffer. Arguments out of the range 0-3 will return 0.

The function Point does not work in text modes.

Speed note: while Point provides valid results, it is quite slow to call repeatedly due to the overhead of additional calculations and checks. Much better performance can be achieved by using direct memory access using the results obtained from ImageInfo and ScreenInfo/ScreenPtr.

Return Value

The return datatype is a ULong.

If the x, y coordinates of a pixel are provided Point returns the color attribute at the specified coordinates, as an 8-bit palette index in 8 bpp indexed modes, a 24-bit RGB value in 16 bpp modes (upper 8 bits unused, limited precision of R,G,B), and a 32-bit RGB or RGBA value in 32 bpp modes (upper 8 bits unused or holding Alpha). Note that it does NOT return a 16-bit value (5 bits R + 6 bits G + 5 bits B).

If the argument is a function index, Point returns one of the graphics cursor coordinates set by the last graphics command.

Argument	Value Returned
0	The current physical x coordinate.
1	The current physical y coordinate.
2	The current view x coordinate. This returns the same value as the POINT(0) function if the WINDOW statement has not been used.
3	The current view y coordinate. This returns the same value as the POINT(1) function if the WINDOW statement has not been used.

Remarks

Usage

coord_x

x coordinate of the pixel

coord_y

y coordinate of the pixel

buffer

the image buffer to read from

function_index

the type of screen coordinate to return: one of the values 0, 1, 2, 3

Differences from QB

• buffer is new to FreeBASIC
• In 16 bpp and 32 bpp modes, a 32-bit value is returned instead of an 8-bit palette index

See also

• PSet - write pixels
• PMap
• Color
• View (Graphics)
• Window

Examples

' Set an appropriate screen mode - 320 x 240 x 8bpp indexed color

ScreenRes 320, 240, 8

' Draw a line using color 12 (light red)

Line (20,20)-(100,100), 12

' Print the color of a point on the line

Print Point(20,20)

' Sleep before the program closes

Sleep

Output:

12

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Category: 2D Drawing Functions
Kind: keyword

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Reproduced from the FreeBASIC Wiki Manual under the GNU Free Documentation License 1.3 — with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. Copyright © the FreeBASIC project and wiki contributors. See License.