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:
