Fig. 1 shows one horizontal row from a monochrome image used on an information screen at a mountain rescue base. The image is stored as one bit per pixel. A...
Question 1 Report
Fig. 1 shows one horizontal row from a monochrome image used on an information screen at a mountain rescue base. The image is stored as one bit per pixel. A 1 means that the pixel is black and a 0 means that the pixel is white. The pixels are numbered from left to right so that a programmer can use the correct binary pattern when updating the image file.
The complete warning symbol contains 24 rows of 8 pixels. A revised program will store 16 symbols of this size in a single file. No compression or metadata is used.
(a) Identify the number of pixels in the row shown in Fig. 1. [2]
(b) Write the 8-bit binary pattern for the row in Fig. 1. [3]
(c) Complete the calculation of the number of bits needed for one complete warning symbol. [4]
(d) Use the image dimensions to calculate the total number of bytes needed for the 16-symbol file. Show your working. [4]
Answer Details
(a) There are eight numbered squares in the row, so it contains 8 pixels. [2]
(b) Read from left to right, using black = 1 and white = 0: black, white, black, black, white, white, black, white becomes 10110010. [3]
(c) Each pixel uses one bit in a monochrome image. Therefore:
\[24\text{ rows}\times8\text{ pixels per row}=192\text{ pixels}=192\text{ bits}\]
[4]
(d) For 16 symbols:
\[16\times24\times8=3072\text{ bits}\]
There are 8 bits in one byte:
\[3072\div8=384\text{ bytes}\]
The file needs 384 bytes. [4]
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