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Technology & Calculator Open Topic
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bwang
Member
Joined: 15 Mar 2009
Posts: 128
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 Posted: 08 Jun 2010 07:16:51 pm Post subject: |
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The following program does not work:
Code:
//This program reads in a 24-bit bmp image file named test.tns in the directory bmpviewer
#include <os.h>
#include "utils.h"
asm(".string \"PRG\"\n");
int main(void)
{
//bitmap header
char* header = (char*) malloc(0x36);
//screen buffer
char* scrbuf = (char*) malloc(SCREEN_BYTES_SIZE);
clearBuf(scrbuf);
//image file
FILE* img;
//loop indices
int i, x, y;
//read the header
img = fopen("/documents/bmpviewer/test.tns", "r");
fread(header, 1, 0x36, img);
//compute some ints (image data size, width, and height) from the header
int bmpsize = header[34] +
256 * header[35] +
65536 * header[36] +
65536 * 256 * header[37];
int w = header[18] +
256 * header[19] +
65536 * header[20] +
65536 * 256 * header[21];
int h = header[22] +
256 * header[23] +
65536 * header[24] +
65536 * 256 * header[25];
//number of pixels
int pxsize = bmpsize / 3;
//allocate byte data and pixel (grayscale) data
char* data = (char*) malloc(bmpsize);
char* pxdata = (char*) malloc(pxsize);
//read in data and close image
fread(data, 1, bmpsize, img);
fclose(img);
//convert RGB to grayscale
for (i = 0; i < pxsize; i++) {
pxdata[i] = (data[3 * i] + data[3 * i + 1] + data[3 * i + 2]) / 48;
}
//draw to the buffer and display it
for (x = 0; x < w; x++) {
for (y = 0; y < h; y++) {
setPixelBuf(scrbuf, x, h - 1 - y, pxdata[w * y + x]);
}
}
refresh(scrbuf);
while (!isKeyPressed(KEY_NSPIRE_ESC));
return 0;
}
When I try reading the file into the "data" array, it reads a few thousand bytes and then stops working. Why is this so?
The program is attached. To run it, place demo-noncas.tns and test.tns in a folder called bmpviewer on the Nspire.
Last edited by Guest on 08 Jun 2010 07:27:49 pm; edited 1 time in total |
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bsl
Advanced Newbie
Joined: 09 Jan 2010
Posts: 94
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| Posted: 08 Jun 2010 11:41:36 pm Post subject: |
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This is a good example of using the printf() call for debugging.
printf() is the oldest debugging tool around.
You may be mixing ints and chars. If you typecast everything to an int it might work as expected.
Also open in binary mode: "rb" instead of "r" , img = fopen("/documents/bmpviewer/test.tns", "rb");
Code:
int bmpsize = header[34] +
256 * header[35] +
65536 * header[36] +
65536 * 256 * header[37];
printf("bmpsize(no typecast)=%d\n",bmpsize); // check emulator console
bmpsize = (int)header[34] +
256 * (int)header[35] +
65536 * (int)header[36] +
65536 * 256 * (int)header[37];
printf("bmpsize(with typecast)=%d\n",bmpsize); // check emulator console
Last edited by Guest on 08 Jun 2010 11:55:02 pm; edited 1 time in total |
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calc84maniac
Elite
Joined: 22 Jan 2007
Posts: 770
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| Posted: 08 Jun 2010 11:54:29 pm Post subject: |
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| Or perhaps these pointers should be unsigned char? |
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bwang
Member
Joined: 15 Mar 2009
Posts: 128
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| Posted: 08 Jun 2010 11:59:39 pm Post subject: |
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Yay! Opening the files as "rb" did the trick :)
calc84maniac: How do you list all the files in a directory, like you did in gbc4nspire?
Last edited by Guest on 09 Jun 2010 12:11:58 am; edited 1 time in total |
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