CS 218 Assignment #11, Part A solution

Description

Purpose: Become more familiar with operating system interaction, file input/output operations, and
file I/O buffering.
Points: 300 (grading will include functionality, documentation, and coding style)
Assignment:
Write a
program that
will create a
thumbnail1
(small,
300×200
image). The
program will
read the
source file
and output file
names from the command line. The program must perform basic error checking on the command line
file names. For example, given an impage file, image.bmp, to create a thumbnail image named
thumb.bmp, the command line might be as follows:
./makeThumb image.bmp thumb.bmp
The required functions include the following:
● Function getImageFileNames() to read and verify the file names from the command line. The
function should check the file names by attempting to open the files. If both files open, the
function should return TRUE and the file descriptors. The function should verify the “.bmp”
extension. If there is an error, the function should display an appropriate error message and
return FALSE.
● Function setImageInfo() to read (original image file), verify, and write (thumbnail file) the
header information. The function must check the signature, color depth, and bitmap size
consistency. Refer to the BMP File Format section. If the original image file information is
correct, the header should updated to reflect the height and width (passed) and the new smaller
thumbnail file size (width * height * 3 + HEADER_SIZE). Once updated, the revised header
can be written to the output file. Additionally, the original width and original height should be
returned to the main (via reference). If all parameters were correct, the function should return
TRUE. If there is an error, the function should display an appropriate error message
(predefined) and return FALSE.
● Function readRow() should return one row of pixels. If a row can be returned, the function
should return the row and return TRUE. If a row can not be returned (because there is no more
data) the function should return FALSE. If there is a read error, the function should dispaly an
appropriate error message (predefined) and return FALSE. To ensure overall efficiency, the
function must perform buffered input with a buffer size of BUFF_SIZE (originally set to
750,000). Note, this will be changed for part B.
1 For more information, refer to: https://en.wikipedia.org/wiki/Thumbnail
● Void function writeRow() should write one row of pixels to the output file. If successful, the
function should return TRUE. If there is a write error, the function should display an
appropriate error message (predefined) and return FALSE. This function is not required to
buffer the output. As such, each row may be written directly to the output file.
Provided Main
The provided main program calls the various functions. The provided main program must not be
changed in any way. All your functions must be in a separate, independently assembled source file.
Note, to help with the initial program testing, it might be best to temporarily skip (comment out) the
calls to the image manipulation statements (in the main).
Assemble and Linking Instructions
You will be provided a main function (makeThumb.cpp) that calls the functions. Your functions
should be in a separate file (a11procs.asm). The files will be assembled individually and linked
together.
When assembling, and linking the files for assignment #10, use the provided makefile to assemble, and
link. Note, only the functions file, a11procs.asm, will be submitted. The submitted functions file
will be assembled and linked with the provided main. As such, do not alter the provided main.
Debugging -> Command Line Arguments
When debugging a program that uses command line arguments, the command line arguments must be
entered after the debugger has been started. The debugger is started normally (ddd ) and
once the debugger comes up, the initial breakpoint can be set. Then, when you are ready to run the
program, enter the command line arguments. This can be done either from the menu (Program -> Run)
or on the GDB Console Window (at bottom) by typing run at the
(gdb) prompt (bottom window).
Buffering
Since many image files can be very large, it would be difficult to pre-allocate enough memory to hold a
complete large image. Further, that memory would be mostly unused for processing smaller images.
To address this, the program will perform buffered input. Specifically, the program should read a full
buffer of BUFF_SIZE bytes (originally set to 750,000). Note, this will be changed for part B.
From that large buffer, the readRow() function would return one row, width × 3 bytes. The next
call to the readRow() function would return the next row. As such, the readRow() function must keep
track of where it is in the buffer. When the buffer is depleted, the readRow() function must re-fill the
buffer by reading BUFF_SIZE bytes from the file. Only after the last row has been returned, should
the readRow() function return a FALSE status.
24-bit Color Depth
For 24-bit color depth, the pixel color is stored as three bytes, a red value (0-255), a green value (0-
255), and a blue value (0-255). The color values are stored in that order. Thus, each pixel is 3 bytes
(or 24-bits). So, for a 800 pixel row, there are 2,400 bytes (800 * 3).
The main sets a row value maximum as 5,000 pixels (or 15,000 bytes). The provided main will
perform this verification and display an appropriate error message as required.
BMP File Format2

The BMP format supports a wide range of different types, including possible compression and 16, 24,
and 32 bit color depths. For our purposes, we will only support uncompressed, 24-bit color BMP files.
Under these restrictions, the header (or initial information) in the file is a 138 byte block containing a
series of data items as follows:
Size Description
2 bytes Signature. Must be ”BM”.
Note, must ensure is “BM” for this assignment.
4 bytes File size (in bytes).
4 bytes Reserved.
4 bytes Size of header. Varies based on compression and color depth.
For an uncompressed, 24-bit color depth, the header is 54
bytes.
4 bytes Offset to start of image data in bytes. May vary based on
compression and color depth.
4 bytes Image width (in pixels).
4 bytes Image height (in pixels).
2 bytes Number of planes in image (typically 1).
2 bytes Number of bits per pixel. Typically 16, 24, or 32.
Note, must ensure is 24 for this assignment.
4 bytes Compression Type (0=none).
Note, must ensure is 0 for this assignment.
4 bytes Size of image in bytes (may vary based on compression types).
100 bytes Miscellaneous (not used for uncompressed, 24-bit color depth).
Since the remaining parts of the program will only work for uncompressed, 24-bit color depth, these
must be verified before the program can perform image manipulations. Specifically, the following
items should be verified:
● File signature is valid (must be “BM” for signature).
● Color depth is 24-bits.
● Image data is not compressed (i.e., compression type must be 0).
● File bitmap block size consistency (file size = size of image in bytes + header size).
Appropriate error message strings are provided in the functions template. Once these are verified, the
header information should be written to the output file.
Example Executions:
The following execution, which includes some errors, will read file image0.bmp, create the thumbnail
image, and place the output image in a file named tmp.bmp.
ed-vm% ./makeThumb
Usage: ./makeThumb
ed-vm%
ed-vm% ./makeThumb img0.bp thm.bmp
Error, invalid source file name. Must be ‘.bmp’ file.
ed-vm% ./makeThumb none .bmp tmp.thm
Error, too many command line arguments.
2 For more information, refer to: http://en.wikipedia.org/wiki/BMP_file_format
ed-vm%
ed-vm% ./makeThumb none.bmp none. bmp
Error, too many command line arguments.
ed-vm%
ed-vm% ./makeThumb img1.bmp thm.bmpp
Error, invalid output file name. Must be ‘.bmp’ file.
ed-vm%
ed-vm% ./makeThumb tmp.bmp
Error, incomplete command line arguments.
ed-vm%
ed-vm% ./makeThumb img4.bmp tmpImg4.bmp
ed-vm%
ed-vm% ./makeThumb test/imgBad1.bmp tmp.bmp
Error, unsupported color depth. Must be 24-bit color.
ed-vm%
ed-vm% ./makeThumb test/imgBad2.bmp tmp.bmp
Error, only non-compressed images are supported.
ed-vm%
ed-vm% ./makeThumb test/imgBad3.bmp tmp.bmp
Error, bitmap block size inconsistent.
ed-vm%
ed-vm% ./makeThumb test/imgBad0.bmp tmp.bmp
Error, invalid file signature.
ed-vm%
Note, a series of image files, including img4.bmp, are provided. However, the program will work on
any uncompressed, 24-bit BMP format file.
Example Ouptut Images
The following table provides some examples of the expected final output.
Example Output
Original Image
img4.bmp
Original Image Size: 5.8 MB
Image thumbnail
tmpImg4.bmp
Original Image Size: 180.1 KB
Submission:
• All source files must assemble and execute on Ubuntu with yasm.
• Submit source files
◦ Submit a copy of the program source file via the on-line submission.
◦ Note, only the functions file (a11procs.asm) will be submitted.
• Once you submit, the system will score the project and provide feedback.
◦ If you do not get full score, you can (and should) correct and resubmit.
◦ You can re-submit an unlimited number of times before the due date/time (at a maximum
rate of 5 submissions per hour).
• Late submissions will be accepted for a period of 24 hours after the due date/time for any given
assignment. Late submissions will be subject to a ~2% reduction in points per an hour late. If
you submit 1 minute – 1 hour late -2%, 1-2 hours late -4%, … , 23-24 hours late -50%. This
means after 24 hours late submissions will receive an automatic 0.
Program Header Block
All source files must include your name, section number, assignment, NSHE number, and program
description. The required format is as follows:
; Name:
; NSHE ID:
; Section: