ON ERROR question

[TerryRitchie]

Hmm... ok, thanks guys. I think I may have used ON ERROR a few times back in the GWBasic days so I wasn't aware of this.

It would be handy though if a label inside of a sub/function could be used. Take the code below for instance, it's the function I created from Steve's code in the other thread concerning gathering color depths. This function will fail if a negative arbitrary number is sent that does not belong to an actual image. I would like to catch that error when _PIXELSIZE encounters it and then simply exit the function, returning a value of 0. If I were to place the label outside of this function then other libraries loading before or after this would cause an error relating to code between subs/functions.

It would also be nice to test for a text mode only image being sent by copying the image and doing a simple PSET to it. If it fails then it's a text mode only image that was passed.

Code: (Select All)

'LIB_IMG_ColorDepth.BM



FUNCTION IMG_ColorDepth% (i AS LONG)



    '+------------------------------------------------+

    '| Returns the color depth of an image passed in. |

    '|                                                |

    '| i - the image handle                          |

    '|                                                |

    '| Returns:  0 : not an image                    |

    '|          32 : 32 bit color image              |

    '|          256 : 256 color image                |

    '|          16 : 16 color image (or text only)  |

    '|                                                |

    '| Note: this function will fail if an image      |

    '|      handle value passed in is less than -1  |

    '|      but does not belong to an actual image.  |

    '+------------------------------------------------+



    DIM c AS INTEGER ' color counter

    DIM p AS INTEGER ' palette counter



    IF i > -2 THEN EXIT FUNCTION '                                not an image, return 0

    IF _PIXELSIZE(i) = 4 THEN '                                  4 bytes per pixel?

        IMG_ColorDepth% = 32 '                                    yes, 32 bit color image

    ELSE '                                                        no, 1 byte per pixel

        p = 0 '                                                  reset palette counter

        c = 0 '                                                  reset color counter

        DO '                                                      begin palette search

            IF _PALETTECOLOR(p, i) <> &HFF000000 THEN c = c + 1 ' increment color counter if color found

            p = p + 1 '                                          increment palette counter

        LOOP UNTIL p = 256 '                                      leave when entire palette searched

        IF c <= 16 THEN '                                        16 colors or less?

            IMG_ColorDepth% = 16 '                                yes, 16 color image

        ELSE '                                                    no, greater than 16

            IMG_ColorDepth% = 256 '                              256 color image

        END IF

    END IF



END FUNCTION