![]() ![]() The following hexadecimal output shows the contents of the file Redbrick.bmp. If it is a bottom-up bitmap, start at the bottom line of the bitmap instead of the top line, still going from left to right, and continue to the top line of the bitmap. Continue until you finish with the entire bitmap. After you reach the right-most pixel in the line, continue with the left-most pixel in the line below. The color of the next pixel to the right is the next n bits in the array, and so forth. The index of the RGBQUAD for the color of the left-most pixel is the first n bits in the color-index array (where n is the number of bits needed to indicate all of the RGBQUAD structures). ![]() To create a color-index array for a top-down bitmap, start at the top line in the bitmap. The Redbrick.bmp, mentioned in About Bitmaps, is a 32x32 bitmap with 16 colors its color-index array is 32 * 32 * 4 = 4096 bits because four bits index 16 colors. For example, an 8x8 black-and-white bitmap has a color-index array of 8 * 8 * 1 = 64 bits, because one bit is needed to index two colors. Thus, the number of bits in the color-index array equals the number of pixels times the number of bits needed to index the RGBQUAD structures. The color-index array associates a color, in the form of an index to an RGBQUAD structure, with each pixel in a bitmap. The RGBQUAD structures specify the RGB intensity values for each of the colors in the device's palette. The members of the BITMAPINFOHEADER, BITMAPV4HEADER, or BITMAPV5HEADER structure specify the width and height of the bitmap, in pixels the color format (count of color planes and color bits-per-pixel) of the display device on which the bitmap was created whether the bitmap data was compressed before storage and the type of compression used the number of bytes of bitmap data the resolution of the display device on which the bitmap was created and the number of colors represented in the data. The members of the BITMAPFILEHEADER structure identify the file specify the size of the file, in bytes and specify the offset from the first byte in the header to the first byte of bitmap data. The bitmap file format is shown in the following illustration. The color table is followed by a second array of indexes into the color table (the actual bitmap data). An array of RGBQUAD structures (also called a color table) follows the bitmap information header structure. The established bitmap file format consists of a BITMAPFILEHEADER structure followed by a BITMAPINFOHEADER, BITMAPV4HEADER, or BITMAPV5HEADER structure. Bitmaps should be saved in a file that uses the established bitmap file format and assigned a name with the three-character. ![]()
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