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November 26, 2008
bitmap processing
Here is the PHP code for changing colors in a bitmap file. This particular example uses a
grayscale file, but it is applicable to full-color files, too.
";_ echo filesize ( $inFile ). "
" ; $in = fopen ( $inFile , 'r' ); // Read header. $c = array (); while ( $i < 14 ) { $c [ $i ]= ord ( fgetc ( $in )); echo $c [ $i ]. " " ; $i ++; } echo "
" ; // Calculate file size. $size = $c [ 4 ] 65536 + $c [ 3 ] 256 + $c [ 2 ]; echo "File size = ". $size. " bytes.
" ; $offset = $c [ 10 ]; echo "Offset to start of image = ". $offset. "
" ; $i = 0 ; while ( $i < 40 ) { $c [ $i ]= ord ( fgetc ( $in )); echo $c [ $i ]. " " ; $i ++; } echo "
Bits per pixel = ". $c [ 14 ]. "
" ; // Go back to beginning of file -- first close it... fclose ( $in ); // Get rows and columns. $cols = $c [ 5 ]* 256 + $c [ 4 ]; $rows = $c [ 9 ]* 256 + $c [ 8 ]; echo "This image has ". $rows. " rows and ". $cols. " columns.
" ; // Total number of pixels. $N = $rows * $cols ; // ... and then re-open it along with output file. $in = fopen ( $inFile , 'r' ); $out = fopen ( $outFile , 'w' ); // Skip to start of image data. for ( $i = 0 ; $i < $offset ; $i ++) { $ch = fgetc ( $in ); fwrite ( $out , $ch , 1 ); } // Now read image bytes. for ( $n = 1 ; $n <= $N ; $n ++) { // Read colors, blue, green, red.
for ( $i = 0 ; $i <= 2 ; $i ++) { $c [ $i ]= fgetc ( $in ); // Here is where you can modify pixel colors. This statement turns on // the red gun to maximum brightness for every pixel. if ( $i == 0 ) $c [ $i ]= chr ( 255 ); fwrite ( $out , $c [ $i ], 1 ); } } echo "Total number of pixels written (rows x columns) = ". $n. "
" ; echo "Here is the last set of three pixels:
" ; echo ord ( $c [ 0 ]). " ". ord ( $c [ 1 ]). " ". ord ( $c [ 2 ]). "
" ; fclose ( $in ); fclose ( $out ); ?>
November 19, 2008
Code to prevent multiple form submission in “account keeper” program.
For reasons I don’t understand, I can’t get the code in your PHP book about
preventing multiple submissions to work with this homework problem. Here is an HTML
document that will work. You have to click on the Reset button before you can submit
another transaction.
**
** Transaction Amount: $
Deposit **** _ _ Withdrawal
Date (mm/dd/yyyy): **
**
October 23, 2008
for ( i = 0 ; i < n ; i ++) { if ( S. charAt ( i )!= "," ) s += S. charAt ( i ); else { // Save the number when you find a comma. A [ j ]= parseFloat ( s );; j ++; s = "" ; } }
October 22, 2008
Last night, the group working on the “blood types” document wanted to be able to
change the background color of their document based on some criterion calculated from a
user’s blood type. Here’s how to do it.
Colors are set by assigning decimal values between 0 and 255 to the red, green,
and blue “guns” (in reference to cathode ray tube technology). You can specify these
values any way you like, but you must then convert them into a hexadecimal string that
can be used to specify the color. For example, a totally black background is #000000 (all
guns off), a white background is #ffffff (all guns at maximum), and a bright fuschia
background is #ff00ff (blue gun turned off). Here’s a function that generates a string
based on three numerical inputs for red, green, and blue guns. The toString() method
converts a number to a string. By default, this method assumes you want the number
represented as a base-10 (decimal) string. If you specify toString(16), the
assumption is that you want a hexadecimal representation of the number, which is what
we need here.
I can’t guarantee that this will work with all browsers. I searched briefly online
for code to do this task, but I didn’t find anything right away so I wrote my own. There
may be other solutions, too, but this one seems to work fine.
**
**
** **
Group project from 21 October: Find all occurrences of a substring in a string.
Untitled
Enter your mutation here:
Enter your sequence here:
Group project from 21 October: blood types
** **
** ** A+ ** ** A- ** ** B+ ** ** B- ** ** AB+ ** ** AB- ** ** O+ ** ** O- **
** Blood type that you can donate to: **
** % of Population with that type of blood: **
** Blood type that you can recieve blood from:
% of Population with that type of blood: **
**
Returning multiple values from a function by storing them in an array.
This is another version of the Document 6.5, circlestuff.htm, in which the area
and circumference are stored in an array, to be returned to the main document. This is
often a better way to return multiple output values than passing a form to the function.
circlestuff2.htm
**
** Circle Stuff **
function circleStuff** ( r ) { var r = parseFloat ( r ); var circle =[]; circle [ 0 ]=( Math. PI * r * r ). toFixed ( 4 ); circle [ 1 ]=( 2 .* Math. PI * r ). toFixed ( 4 ); return circle ; } **
** Circle Stuff ** ** Enter radius, then press tab key or click on "area" box.
radius (cm):
area (cm **** 2 **** ):
circumference(cm): **
**
Parsing strings:
Here are a couple of examples for manipulating strings. The first example could
represent a start at code that extracts numbers from a string of characters entered into a
type=”text” box, with numbers separated by commas. For example, if you entered
your goal would be to extract the four real numbers and store them in an array.
Example 1:
**
**
**** home **
**
frameDescription.htm
**
1"> ** How this image was created. **
** This image was created in Windows' Paint program. **** Click here to return. **
**
frameMain.htm
**
** A simple frameset document **
**
gossip.htm
**
** Gossip Column **
document**. write ( "This document last modified on " + document. lastModified + "." ) **
** This is where gossip goes!!! **
** Can you **** believe **** that...??? **
**
homeFrame.htm
**
** Gossip Column ****
** document**. write ( "This document last modified on " + document. lastModified + "." ) **
** This is where gossip goes!!! **
** Can you **** believe **** that...??? **
**
photoGallery.htm
**
** A picture gallery **
** Here is the picture gallery. **
**
frame.gif
picture.gif
