cropping an image script

In the following php script, the function takes the original file and crops to the destination file. I've ran the script using a .png file and a .jpg file. The .png works fine whereas the .jpeg file returns only part of the image along with a blue rectangle. For instance - where the original image is a 200 x 300 jpeg called: 1_data.jpeg and the destination iamge is 75x75 called: 2_data.jpeg and starting at the x,y coordinates of 0,0 - the script returns a 75x 75 file but only a sliver of the .jpg image is within the 75x75 blue square. Any help will be of assistance. Thank you. Tony Ritter ........................................................ The following is the php cropping script (with author credit): <? // // image crop fuction ..... Duck@obala.net // info at http://obala.net/en // // Yes the proses could be executed with imagecopyresized build-in function // but with this function you get the idea of how an image color set is constructed // // $cropX = source starting X // $cropY = source starting Y // $cropW = crop weigth // $cropH = crop heigh // $source = source filename // $destination = destination filename // $type = image type function im_crop($cropX,$cropY,$cropH,$cropW,$source,$destination,$type='jpeg') { // switch known types and open source image switch ($type) { case 'wbmp': $sim = ImageCreateFromWBMP($source); break; case 'gif': $sim = ImageCreateFromGIF($source); break; case 'png': $sim = ImageCreateFromPNG($source); break; default: $sim = ImageCreateFromJPEG($source); break; } // create the destination image $dim = imagecreate($cropW, $cropH); // pass trought pixles of source image for ( $i=$cropY; $i<($cropY+$cropH); $i++ ) { for ( $j=$cropX; $j<($cropX+$cropW); $j++ ) { // get RGB color info about a pixel in the source image $color = imagecolorsforindex($sim, imagecolorat($sim, $j, $i)); // insert the color in the color index of the new image $index = ImageColorAllocate($dim, $color['red'], $color['green'], $color['blue']); // plots a pixel in the new image with that color imagesetpixel($dim, $j-$cropX, $i-$cropY, $index); } } // whe dont need the sorce image anymore imagedestroy($sim); // switch known types and save switch ($type) { case 'wbmp': ImageWBMP($dim, $destination); break; case 'gif': ImageGIF($dim, $destination); break; case 'png': ImagePNG($dim, $destination); break; default: ImageJPEG($dim, $destination); break; } // free the used space of the source image imagedestroy($dim); } // example im_crop(0,0,75,75,'1_data.jpeg','2_data.jpeg','jpeg'); ?>