ImageInfofunction

Retrieves information about an image

Syntax

Declare Function ImageInfo ( ByVal image As Const Any Ptr, ByRef width As Long = 0, ByRef height As Long = 0, ByRef bypp As Long = 0, ByRef pitch As Long = 0, ByRef pixdata As Any Ptr = 0, ByRef size As Long = 0 ) As Long

Declare Function ImageInfo ( ByVal image As Const Any Ptr, ByRef width As LongInt, ByRef height As LongInt, ByRef bypp As LongInt = 0, ByRef pitch As LongInt = 0, ByRef pixdata As Any Ptr = 0, ByRef size As LongInt = 0 ) As Long

Parameters

Name		Description
`image`		The address of the image.
`width`		Stores the width of the image, in pixels.
`height`		Stores the height of the image, in pixels.
`bypp`		Stores the bytes per pixel of the image - i.e. the size of a single pixel, in bytes.
`pitch`		Stores the pitch of the image - i.e. the size of each scanline (row), in bytes. Note that this may be more than just
`width * bypp`		, because the scanlines may be padded to allow them to be aligned better in memory.
`pixdata`		Stores the address of the start of the first scanline of the image.
`size`		Stores the size of the image in memory, in bytes.

Return value

If image doesn't point to a valid image, one (1) is returned. Otherwise, width, height, bypp, pitch, pixdata and size are assigned appropriate values, and zero (0) is returned.

Description

ImageInfo provides various information about an image, such as its dimensions and color depth, but also provides you with the information you need to directly access all the pixel data in the pixel buffer.

It can also provide the size of the image in memory, which is useful for allocating memory to copy the existing image, or to write the image to a file.

ImageInfo is an alternative way to access the main characteristics of an image, rather than directly accessing the internal FB.IMAGE structure (defined in fbgfx.bi) through a typed pointer to member data.

The error code returned by ImageInfo can be checked using Err in the next line. The function version of ImageInfo returns directly the error code as a 32 bit Long.

Remarks

Usage



in the LONG (or INTEGER<32>) version of the function:

result = ImageInfo( image [, [ width ] [, [ height ] [, [ bypp ] [, [ pitch ] [ , [ pixdata ] [, size ]]]]]] )

in the LONGINT (or INTEGER<64>) version of the function:

result = ImageInfo( image , width , height [, [ bypp ] [, [ pitch ] [ , [ pixdata ] [, size ]]]] )

Version

Before fbc 1.08.0:

Syntax:

Declare Function ImageInfo ( ByVal image As Any Ptr, ByRef width As Integer = 0, ByRef height As Integer = 0, ByRef bypp As Integer = 0, ByRef pitch As Integer = 0, ByRef pixdata As Any Ptr = 0, ByRef size As Integer = 0 ) As Long

Usage:

result = ImageInfo( image [, [ width ] [, [ height ] [, [ bypp ] [, [ pitch ] [, [ pixdata ] [, size ]]]]]] )

Dialect Differences

Not available in the -lang qb dialect unless referenced with the alias __Imageinfo.

Differences from QB

New to FreeBASIC

Example

'' pixelptr(): use imageinfo() to find the pointer to a pixel in the image

'' returns null on error or x,y out of bounds

Function pixelptr(ByVal img As Any Ptr, ByVal x As Integer, ByVal y As Integer) As Any Ptr



    Dim As Long w, h, bypp, pitch

    Dim As Any Ptr pixdata

    Dim As Long result

    

    result = ImageInfo(img, w, h, bypp, pitch, pixdata)

    

    If result = 0 Then '' seems like a valid image

        If x < 0 Or x >= w Then Return 0

        If y < 0 Or y >= h Then Return 0

        Return pixdata + y * pitch + x * bypp

    Else

        Return 0

    End If

    

End Function



'' usage example:



'' 320*200 graphics screen, 8 bits per pixel

ScreenRes 320, 200, 8



Dim As Any Ptr ip '' image pointer



Dim As Byte Ptr pp '' pixel pointer (use byte for 8 bits per pixel)



ip = ImageCreate(32, 32) '' create an image (32*32, 8 bits per pixel)



If ip <> 0 Then



    '' draw a pattern on the image

    For y As Integer = 0 To 31



        For x As Integer = y - 5 To y + 5 Step 5



            '' find the pointer to pixel at x,y position

            '' note: this is inefficient to do for every pixel!

            pp = pixelptr(ip, x, y)



            '' if success, plot a value at the pixel

            If (pp <> 0) Then *pp = 15



        Next x



    Next y



    '' put the image and draw a border around it

    Put (10, 10), ip, PSet

    Line (9, 9)-Step(33, 33), 4, b



    '' destroy the image to reclaim memory

    ImageDestroy ip



Else

    Print "Error creating image!"

End If



Sleep

'' Create 32-bit graphics screen and image.

ScreenRes 320, 200, 32

Dim image As Any Ptr = ImageCreate( 64, 64 )



Dim pitch As Long

Dim pixels As Any Ptr



'' Get enough information to iterate through the pixel data.

If 0 <> ImageInfo( image, ,,, pitch, pixels ) Then

    Print "unable to retrieve image information."

    Sleep

    End

End If



'' Draw a pattern on the image by directly manipulating pixel memory.

For y As Integer = 0 To 63

    Dim row As ULong Ptr = pixels + y * pitch

    

    For x As Integer = 0 To 63

        row[x] = RGB(x * 4, y * 4, (x Xor y) * 4)

    Next x

Next y



'' Draw the image onto the screen.

Put (10, 10), image



ImageDestroy( image )



Sleep

Reference

Documented in KeyPgImageInfo.html