I am writing a longer program and I found myself needing to read a .bmp file into an array in a specific way so that the rest of the program can use it without extensive rewrites. I failed to find older answers that would resolve my problem, and I am pretty much at the beginner stages.
The image I am trying to read is used to create a text font, so I want to read it character by character into an array, where the pixels belonging to one character are added in order to a 2d bool (true if pixel is not black) array [character_id] [pixel_n]. The dimensions of characters are predetermined and known, and the file is cropped so that they all appear in a single row with no unaccounted margins.
This is the specific file I am trying to read, though here it might not show up as .bmp
As an example, shown here, I want to read the pixels in the order of the yellow line, then jump to another character. For clarity each character is 5px wide and 11px high, with 1px of margin on both sides horizontally.
Based on what I was able to find, I have written a function to do it, but I fail to make it work as intended, as far as I can tell even the pixel values are not being read correctly:
void readBMP(char* filename)
{
int i;
FILE* f = fopen(filename, "rb");
unsigned char info[54];
// read the 54-byte header
fread(info, sizeof(unsigned char), 54, f);
// extract image height and width from header
int width = *(int*)&info[18];
int height = *(int*)&info[22];
// number of pixels in total
int size = 3 * width * height;
unsigned char* data = new unsigned char[size];
// number of characters to read
int counter1 = size / ((font_width + 2) * font_height) / 3 ;
// read the rest of the data at once
fread(data, sizeof(unsigned char), size, f);
fclose(f);
//loop that goes from character to character
for(int i = 0; i < counter1; i++)
{
int tmp = 0;
//loop that reads one character into font_ref array
for(int j = 0; j < font_height; j++)
{
//loop for each row of a character
for(int k = 0; k < font_width; k++)
{
int w = static_cast<int>(data[3*(j*(font_width+2)*(counter1) + i*(font_width + 2) + 1 + k + j*font_width + j)-1]);
if( w != 0 )
font_ref [i][(tmp)] = 1;
else
font_ref [i][(tmp)] = 0;
tmp++;
}
}
}
}
(bool font_ref [150][font_width*font_height]; is the array where the font is being loaded and stored)
this code reads something, but the result is a seemingly random mess and I am unable to resolve that. Here is an example of lowercase alphabet printed using another function in the program, where white pixels represent true bools. I am aware that some libraries exist to work with graphical files, however in this program I wanted to possibly avoid that to learn more lower-level things, and the goal is rather limited and specific.
Thank you in advance for any help with the issue.
The main errors are in the offset computation for a pixel in the bitmap data:
int w = static_cast<int>(data[3*(j*(font_width+2)*(counter1) + i*(font_width + 2) + 1 + k + j*font_width + j)-1]);
j*(font_width+2)*(counter1) - This doesn't take into account that
although you say the file is cropped, there is extra black space to the right of the last character cell, so the true width must be used;
(as drescherjm and user3386109 mentioned) padding bytes are appended to the rows so that their length is a multiple of four bytes.
+ j*font_width + j)-1 - This part makes no sense - perhaps you tried to compensate the above errors.
This would be correct:
int w = data[j*(3*width+3&~3)+3*(i*(font_width+2)+1+k)];
Related
I am accessing the image like so:
pDoc = GetDocument();
int iBitPerPixel = pDoc->_bmp->bitsperpixel; // used to see if grayscale(8 bits) or RGB (24 bits)
int iWidth = pDoc->_bmp->width;
int iHeight = pDoc->_bmp->height;
BYTE *pImg = pDoc->_bmp->point; // pointer used to point at pixels in the image
int Wp = iWidth;
const int area = iWidth * iHeight;
int r; // red pixel value
int g; // green pixel value
int b; // blue pixel value
int gray; // gray pixel value
BYTE *pImgGS = pImg; // grayscale image pixel array
and attempting to change the rgb image to gray like so:
// convert RGB values to grayscale at each pixel, then put in grayscale array
for (int i = 0; i<iHeight; i++)
for (int j = 0; j<iWidth; j++)
{
r = pImg[i*iWidth * 3 + j * 3 + 2];
g = pImg[i*iWidth * 3 + j * 3 + 1];
b = pImg[i*Wp + j * 3];
r * 0.299;
g * 0.587;
b * 0.144;
gray = std::round(r + g + b);
pImgGS[i*Wp + j] = gray;
}
finally, this is how I try to draw the image:
//draw the picture as grayscale
for (int i = 0; i < iHeight; i++) {
for (int j = 0; j < iWidth; j++) {
// this should set every corresponding grayscale picture to the current picture as grayscale
pImg[i*Wp + j] = pImgGS[i*Wp + j];
}
}
}
original image:
and the resulting image that I get is this:
First check if image type is 24 bits per pixels.
Second, allocate memory to pImgGS;
BYTE* pImgGS = (BTYE*)malloc(sizeof(BYTE)*iWidth *iHeight);
Please refer this article to see how bmp data is saved. bmp images are saved upside down. Also, first 54 byte of information is BITMAPFILEHEADER.
Hence you should access values in following way,
double r,g,b;
unsigned char gray;
for (int i = 0; i<iHeight; i++)
{
for (int j = 0; j<iWidth; j++)
{
r = (double)pImg[(i*iWidth + j)*3 + 2];
g = (double)pImg[(i*iWidth + j)*3 + 1];
b = (double)pImg[(i*iWidth + j)*3 + 0];
r= r * 0.299;
g= g * 0.587;
b= b * 0.144;
gray = floor((r + g + b + 0.5));
pImgGS[(iHeight-i-1)*iWidth + j] = gray;
}
}
If there is padding present, then first determine padding and access in different way. Refer this to understand pitch and padding.
double r,g,b;
unsigned char gray;
long index=0;
for (int i = 0; i<iHeight; i++)
{
for (int j = 0; j<iWidth; j++)
{
r = (double)pImg[index+ (j)*3 + 2];
g = (double)pImg[index+ (j)*3 + 1];
b = (double)pImg[index+ (j)*3 + 0];
r= r * 0.299;
g= g * 0.587;
b= b * 0.144;
gray = floor((r + g + b + 0.5));
pImgGS[(iHeight-i-1)*iWidth + j] = gray;
}
index =index +pitch;
}
While drawing image,
as pImg is 24bpp, you need to copy gray values thrice to each R,G,B channel. If you ultimately want to save grayscale image in bmp format, then again you have to write bmp data upside down or you can simply skip that step in converting to gray here:
pImgGS[(iHeight-i-1)*iWidth + j] = gray;
tl; dr:
Make one common path. Convert everything to 32-bits in a well-defined manner, and do not use image dimensions or coordinates. Refactor the YCbCr conversion ( = grey value calculation) into a separate function, this is easier to read and runs at exactly the same speed.
The lengthy stuff
First, you seem to have been confused with strides and offsets. The artefact that you see is because you accidentially wrote out one value (and in total only one third of the data) when you should have written three values.
One can get confused with this easily, but here it happened because you do useless stuff that you needed not do in the first place. You are iterating coordinates left to right, top-to-bottom and painstakingly calculate the correct byte offset in the data for each location.
However, you're doing a full-screen effect, so what you really want is iterate over the complete image. Who cares about the width and height? You know the beginning of the data, and you know the length. One loop over the complete blob will do the same, only faster, with less obscure code, and fewer opportunities of getting something wrong.
Next, 24-bit bitmaps are common as files, but they are rather unusual for in-memory representation because the format is nasty to access and unsuitable for hardware. Drawing such a bitmap will require a lot of work from the driver or the graphics hardware (it will work, but it will not work well). Therefore, 32-bit depth is usually a much better, faster, and more comfortable choice. It is much more "natural" to access program-wise.
You can rather trivially convert 24-bit to 32-bit. Iterate over the complete bitmap data and write out a complete 32-bit word for each 3 byte-tuple read. Windows bitmaps ignore the A channel (the highest-order byte), so just leave it zero, or whatever.
Also, there is no such thing as a 8-bit greyscale bitmap. This simply doesn't exist. Although there exist bitmaps that look like greyscale bitmaps, they are in reality paletted 8-bit bitmaps where (incidentially) the bmiColors member contains all greyscale values.
Therefore, unless you can guarantee that you will only ever process images that you have created yourself, you cannot just rely that e.g. the values 5 and 73 correspond to 5/255 and 73/255 greyscale intensity, respectively. That may be the case, but it is in general a wrong assumption.
In order to be on the safe side as far as correctness goes, you must convert your 8-bit greyscale bitmaps to real colors by looking up the indices (the bitmap's grey values are really indices) in the palette. Otherwise, you could be loading a greyscale image where the palette is the other way around (so 5 would mean 250 and 250 would mean 5), or a bitmap which isn't greyscale at all.
So... you want to convert 24-bit and you want to convert 8-bit bitmaps, both to 32-bit depth. That means you do all the annoying what-if stuff once at the beginning, and the rest is one identical common path. That's a good thing.
What you will be showing on-screen is always a 32-bit bitmap where the topmost byte is ignored, and the lower three are all the same value, resulting in what looks like a shade of grey. That's simple, and simple is good.
Note that if you do a BT.601 style YCbCr conversion (as indicated by your use of the constants 0.299, 0.587, and 0.144), and if your 8-bit greyscale images are perceptive (this is something you must know, there is no way of telling from the file!), then for 100% correctness, you need to to the inverse transformation when converting from paletted 8-bit to RGB. Otherwise, your final result will look like almost right, but not quite. If your 8-bit greycales are linear, i.e. were created without using the above constants (again, you must know, you cannot tell from the image), you need to copy everything as-is (here, doing the conversion would make it look almost-but-not-quite right).
About the RGB-to-greyscale conversion, you do not need an extra greyscale bitmap just to hold the values that you never need again afterwards. You can read the three color values from the loaded bitmap, calculate Y, and directly build the 32-bit ARGB word, which you then write out to the final bitmap. This saves one entirely useless round-trip to memory which is not necessary.
Something like this:
uint32_t* out = (uint32_t*) output_bitmap_data;
for(int i = 0; i < inputSize; i+= 3)
{
uint8_t Y = calc_greyscale(in[0], in[1], in[2]);
*out++ = (Y<<16) | (Y<<8) | Y;
}
Alternatively, you can also do the from-whatever-to-32 conversion, and then do the to-greyscale conversion in-place there. This, in turn, introduces an extra round-trip to memory, but the code becomes much, much easier overall.
I'm developing a uni project for reading the image data of P6-type, 255-depth .ppm images. The problem I encounter is that when I try to print the average values of each color (R,G,B) for an Image, the output I get is wrong (the proffessor has given us an output file which says what float values to expect for each given image).
Now, I'm at a loss here. Through many checks, I have concluded that the function reads the whole data from the image, without leaving out pixels or whatever, converts them correctly from 0-255 to 0.f - 1.f values (by dividing with 255.0), adds every red, every green and every blue value to three seperate counters and then divides them by the Width*Height of the given image to get the desired average brightness of each colour. I will provide part of the function that does this process for calculating the average red for a 960*642 Image (sorry for the hardcoded stuff, it's just there for debugging purposes).
The output I get for this is 0.58... when it should be 0.539068. seekg() is called with 14 as an argument because position 14 is the last space after the header and before the data. Could you provide any insight to why this isn't working as expected? One thing I found through the checks is the sum I get after adding all the red float values, is not a float but an int. Possible loss of data? I'm grasping at straws here.
Here is the code:
std::ifstream infile;
infile.open("Image02.ppm", std::ios::in | std::ios::binary);
const unsigned char* buffer;
float * data_ptr;
infile.seekg(0, std::ios::end);
int length = infile.tellg(); //calculating length of data
buffer = new unsigned char[length];
ptr = new unsigned char[length];
data_ptr = new float[length];
infile.seekg(14, std::ios::beg); //restoring pointer to the start of data stream
infile.read((char*)buffer, length); //reading the image
for (int i = 0; i < length; i++){ //casting the char data to floats to get the 0-255 values
data_ptr[i] = ((float)buffer[i]);
data_ptr[i] = data_ptr[i] / 255.f; // converting to 0.0 - 1.0
}
int j = 0;
float a = 0.f;
while (j < length){ //calculating sum of red pixel values
a = a + data_ptr[j];
j = j + 3;
}
std::cout << a / (960*642); //calculating average
FYI, PPM image files that are P6 have their image data stored from left to right, with the first line being line 0 and the last line of the image being the last. They are structured like this R G B R G B R G B so on, where the first RGB correspond to the first pixel and so forth.
Thanks in advance!
You need pixels only for average calculation.
But in your source code, additional 14 garbage values are being used.
I guess it's such an easy question (I'm coming from Java), but I can't figure out how it works.
I simply want to increment an vector element by one. The reason for this is, that I want to compute a histogram out of image values. But whatever I try I just can accomplish to assign a value to the vector. But not to increment it by one!
This is my histogram function:
void histogram(unsigned char** image, int height,
int width, vector<unsigned char>& histogramArray) {
for (int i = 0; i < width; i++) {
for (int j = 0; j < height; j++) {
// histogramArray[1] = (int)histogramArray[1] + (int)1;
// add histogram position by one if greylevel occured
histogramArray[(int)image[i][j]]++;
}
}
// display output
for (int i = 0; i < 256; i++) {
cout << "Position: " << i << endl;
cout << "Histogram Value: " << (int)histogramArray[i] << endl;
}
}
But whatever I try to add one to the histogramArray position, it leads to just 0 in the output. I'm only allowed to assign concrete values like:
histogramArray[1] = 2;
Is there any simple and easy way? I though iterators are hopefully not necesarry at this point, because I know the exakt index position where I want to increment something.
EDIT:
I'm so sorry, I should have been more precise with my question, thank you for your help so far! The code above is working, but it shows a different mean value out of the histogram (difference of around 90) than it should. Also the histogram values are way different than in a graphic program - even though the image values are exactly the same! Thats why I investigated the function and found out if I set the histogram to zeros and then just try to increase one element, nothing happens! This is the commented code above:
for (int i = 0; i < width; i++) {
for (int j = 0; j < height; j++) {
histogramArray[1]++;
// add histogram position by one if greylevel occured
// histogramArray[(int)image[i][j]]++;
}
}
So the position 1 remains 0, instead of having the value height*width. Because of this, I think the correct calculation histogramArray[image[i][j]]++; is also not working properly.
Do you have any explanation for this? This was my main question, I'm sorry.
Just for completeness, this is my mean function for the histogram:
unsigned char meanHistogram(vector<unsigned char>& histogram) {
int allOccurences = 0;
int allValues = 0;
for (int i = 0; i < 256; i++) {
allOccurences += histogram[i] * i;
allValues += histogram[i];
}
return (allOccurences / (float) allValues) + 0.5f;
}
And I initialize the image like this:
unsigned char** image= new unsigned char*[width];
for (int i = 0; i < width; i++) {
image[i] = new unsigned char[height];
}
But there shouldn't be any problem with the initialization code, since all other computations work perfectly and I am able to manipulate and safe the original image. But it's true, that I should change width and height - since I had only square images it didn't matter so far.
The Histogram is created like this and then the function is called like that:
vector<unsigned char> histogramArray(256);
histogram(array, adaptedHeight, adaptedWidth, histogramArray);
So do you have any clue why this part histogramArray[1]++; don't increases my histogram? histogramArray[1] remains 0 all the time! histogramArray[1] = 2; is working perfectly. Also histogramArray[(int)image[i][j]]++; seems to calculate something, but as I said, I think it's wrongly calculating.
I appreciate any help very much! The reason why I used a 2D Array is simply because it is asked for. I like the 1D version also much more, because it's way simpler!
You see, the current problem in your code is not incrementing a value versus assigning to it; it's the way you index your image. The way you've written your histogram function and the image access part puts very fine restrictions on how you need to allocate your images for this code to work.
For example, assuming your histogram function is as you've written it above, none of these image allocation strategies will work: (I've used char instead of unsigned char for brevity.)
char image [width * height]; // Obvious; "char[]" != "char **"
char * image = new char [width * height]; // "char*" != "char **"
char image [height][width]; // Most surprisingly, this won't work either.
The reason why the third case won't work is tough to explain simply. Suffice it to say that a 2D array like this will not implicitly decay into a pointer to pointer, and if it did, it would be meaningless. Contrary to what you might read in some books or hear from some people, in C/C++, arrays and pointers are not the same thing!
Anyway, for your histogram function to work correctly, you have to allocate your image like this:
char** image = new char* [height];
for (int i = 0; i < height; ++i)
image[i] = new char [width];
Now you can fill the image, for example:
for (int i = 0; i < height; ++i)
for (int j = 0; j < width; ++j)
image[i][j] = rand() % 256; // Or whatever...
On an image allocated like this, you can call your histogram function and it will work. After you're done with this image, you have to free it like this:
for (int i = 0; i < height; ++i)
delete[] image[i];
delete[] image;
For now, that's enough about allocation. I'll come back to it later.
In addition to the above, it is vital to note the order of iteration over your image. The way you've written it, you iterate over your columns on the outside, and your inner loop walks over the rows. Most (all?) image file formats and many (most?) image processing applications I've seen do it the other way around. The memory allocations I've shown above also assume that the first index is for the row, and the second is for the column. I suggest you do this too, unless you've very good reasons not to.
No matter which layout you choose for your images (the recommended row-major, or your current column-major,) it is in issue that you should always keep in your mind and take notice of.
Now, on to my recommended way of allocating and accessing images and calculating histograms.
I suggest that you allocate and free images like this:
// Allocate:
char * image = new char [height * width];
// Free:
delete[] image;
That's it; no nasty (de)allocation loops, and every image is one contiguous block of memory. When you want to access row i and column j (note which is which) you do it like this:
image[i * width + j] = 42;
char x = image[i * width + j];
And you'd calculate the histogram like this:
void histogram (
unsigned char * image, int height, int width,
// Note that the elements here are pixel-counts, not colors!
vector<unsigned> & histogram
) {
// Make sure histogram has enough room; you can do this outside as well.
if (histogram.size() < 256)
histogram.resize (256, 0);
int pixels = height * width;
for (int i = 0; i < pixels; ++i)
histogram[image[i]]++;
}
I've eliminated the printing code, which should not be there anyway. Note that I've used a single loop to go through the whole image; this is another advantage of allocating a 1D array. Also, for this particular function, it doesn't matter whether your images are row-major or column major, since it doesn't matter in what order we go through the pixels; it only matters that we go through all the pixels and nothing more.
UPDATE: After the question update, I think all of the above discussion is moot and notwithstanding! I believe the problem could be in the declaration of the histogram vector. It should be a vector of unsigned ints, not single bytes. Your problem seems to be that the value of the vector elements seem to stay at zero when your simplify the code and increment just one element, and are off from the values they need to be when you run the actual code. Well, this could be a symptom of numeric wrap-around. If the number of pixels in your image are a a multiple of 256 (e.g. 32x32 or 1024x1024 image) then it is natural that the sum of their number would be 0 mod 256.
I've already alluded to this point in my original answer. If you read my implementation of the histogram function, you see in the signature that I've declared my vector as vector<unsigned> and have put a comment above it that says this victor counts pixels, so its data type should be suitable.
I guess I should have made it bolder and clearer! I hope this solves your problem.
I'd like to write a normal map to a .bmp file, so I've implemented a simple .bmp writer first:
void BITMAPLOADER::writeHeader(std::ofstream& out, int width, int height)
{
BITMAPFILEHEADER tWBFH;
tWBFH.bfType = 0x4d42;
tWBFH.bfSize = 14 + 40 + (width*height*3);
tWBFH.bfReserved1 = 0;
tWBFH.bfReserved2 = 0;
tWBFH.bfOffBits = 14 + 40;
BITMAPINFOHEADER tW2BH;
memset(&tW2BH,0,40);
tW2BH.biSize = 40;
tW2BH.biWidth = width;
tW2BH.biHeight = height;
tW2BH.biPlanes = 1;
tW2BH.biBitCount = 24;
tW2BH.biCompression = 0;
out.write((char*)(&tWBFH),14);
out.write((char*)(&tW2BH),40);
}
bool TERRAINLOADER::makeNormalmap(unsigned int width, unsigned int height)
{
std::ofstream file;
file.open("terrainnormal.bmp");
if(!file)
{
file.close();
return false;
}
bitmaploader.writeHeader(file,width,height);
for(int y = 0; y < height; y++)
{
for(int x = 0; x < width; x++)
{
file << static_cast<unsigned char>(255*x/height); //(unsigned char)((getHeight(float(x)/float(width),float(y)/float(height))));
file << static_cast<unsigned char>(0); //(unsigned char)((getHeight(float(x)/float(width),float(y)/float(height))));
file << static_cast<unsigned char>(0); //(unsigned char)((getHeight(float(x)/float(width),float(y)/float(height))));
};
};
file.close();
return true;
};
The writeHeader(...) function is from SO, from a solved,working post. (I've forgot the name of it)
The getHeight(...) is using bicubic interpolation, so I can write it to big resolution images, and it stays smooth. It will be also used for collision detection and now is used as a LOD factor for my clipmaps.
Now the problem is that this outputs a distorted image. The pictures will tell everything I think:
The expected/distorted result(s):
for the heightmap: I have the function that describes a mesh: getHeight(x,z). It gives back the correct results because I've tested it with shaders (by sending heights as vertex attribs) too. The image downloaded from internet:
And with the y(x,z) function values written to a .BMP: (the commented out part of the code):
With a simple function: file << static_cast<unsigned char>(255*(float)x/height)
which should be a simple blend from black to white to the right.
I used an image size of 256 x 256, because I've read it should be multiple of 4. I CAN use libraries, but I'd like to solve this problem without one. So, what caused this distortion?
EDIT:
On the last image some lines are also colored, but they shouldn't be. This post is similar, but my heightmap is not distorted linearly as in this post: Image Distortion with Lock Bits
EDIT:
Another strange issue is when I don't make all colors the same, it get's distorted in colors too. For example set only the RED to the heights, and leave G and B 0, it became not only RED, but a noisy colored heightmap.
EDIT /comments/
If I understood them right, there's the size of the header, then comes my pixel data. Now before the pixel data there must be 4 * n bytes. So that padding mean after the header I put some more data that fills the place.
For example assuming (I will look up hot to get it exactly) my header is 55 bytes, then I should add 1 more byte to it because 55+1 = 56 and 4|56.
So
file << static_cast<unsigned char>('a');
for(int y = 1; y <= width; y++)
{
for(int x = 1; x <= height; x++)
{
file << static_cast<unsigned char>(x);
file << static_cast<unsigned char>(x);
file << static_cast<unsigned char>(x);
};
};
should be correct.
But I realized the real issue (as Jigsore commented). When I cast from int to char, it seems like a 1 digit number becomes 1 byte, 2 digits number 2, and 3 digits 3 bytes. Clamping the height to 3 digits works well, but the image is a bit whitey, because 'darkest' color becomes (100,100,100) instead of (0,0,0). Also, this is the cause of the non-regular distortion, because it depends on how many 'hills' or 'mountains' are there in one row. How can I solve this, and I hope the last problem? I don't want to compress the image to 100-256 range.;)
Open your file in binary mode.
Under Windows, if you open a file in the default text mode, it will write an extra 0x0d (Return) character after every 0x0a (Linefeed) that gets written out. The first time this happens it will change the colors of the following pixels, as the RGB order gets out of alignment. After it happens 3 times you'll be off by a full pixel.
Yes i have been through the other questions that are related to this, but i found them not much help. They were some help but i am still a bit confused. So here what what i need to do:
We have a 132x65 screen. I have a 132x65 .bmp. I want to go through the .bmp and separate it into little 1x8 columns to get the binary of that 32-bit column. Then do that 132 times across, and do that 9 times down. Anything that is not white should be counted as a bit. example:
If the top left pixel of the picture is any color that is not white and the 7 pixels below that are white then that would be the first element of the array, the hex of that number, so the array would look like this:
array [] = { 0x01 } and then it would continue to fill through those 132 columns and then do it again for 9 "sections" of rows. And the file result would be ONLY that array in a separate file.
I understand the header format for this, i have read the wiki article on .bmp file formats, my main problem is i don't really know how to interact with the .bmp when i actually want it to go inside and interact with each pixel from the image. I really dont need the whole thing, but maybe just an example of grabbing each pixel from the .bmp and outputting the color of the pixel into a file or something. My c++ is a little rusty (been doing java and javscript lately).
If you want to read a known format BMP and don't care about how it's done (ie, internal-only thing) you can just take the BMP, ignore the header and use it as a pixel array. It is stored line by line starting at the bottom left. There are some detail snags for how it's packed but in my experience if you take a 32bpp image it can be completely ignored.
As a really simple example:
unsigned int *buffer;
void readfile() {
FILE *f = fopen("file.bmp", "rb");
buffer = new unsigned int[132*65];
fseek(f, 54);
fread(buffer, 132*65*4, 1, f);
fclose(f);
}
unsigned int getpixel(int x, int y) {
//assuming your x/y starts from top left, like I usually do
return buffer[(64 - y) * 132 + x];
}
I had the same problem, but by reading BMP file format description I wrote a function that reads a .BMP file and stores it into a array.
Maybe this function can help you:
unsigned int PIC::BinToNum(char *b,int bytes)
{
unsigned int tmpx = 0;
unsigned int pw = 1;
for(int i=0;i<bytes;i++)
{
tmpx += ((unsigned char)b[i]* pw);
pw = pw * 256;
}
return tmpx;
}
int PIC::Open(const char *path)
{
int pad = 0;
unsigned int sof = 0;
unsigned int tx = 0;
char tmp[4] = {0,0,0,0};
fstream file;
file.open(path,ios::in);
if(file.fail())
{
width=height=ColorBits=size=0;
return -1;
}
else
{
file.seekg(0,ios::beg);
file.read(tmp,2);
if(!(tmp[0] == 66 && tmp[1] == 77))
{
width=height=ColorBits=size=0;
return 0;
}
else
{
file.seekg(2,ios::beg); // 0x2 size
file.read(tmp,4);
size = BinToNum(tmp,4);
file.seekg(18,ios::beg); // 0x12 width
file.read(tmp,4);
width = BinToNum(tmp,4);
file.seekg(22,ios::beg); // 0x16 height
file.read(tmp,4);
height = BinToNum(tmp,4);
file.seekg(28,ios::beg); // 0x1C Bits per Pixel
file.read(tmp,2);
ColorBits = BinToNum(tmp,2);
file.seekg(10,ios::beg); // 0x0A start offset
file.read(tmp,4);
sof=BinToNum(tmp,4);
file.seekg(34,ios::beg); // 0x22 Padding
file.read(tmp,4);
pad = BinToNum(tmp,4);
pad = (int)(pad / height); // Compute Spacing in each row
pad = pad - (width*ColorBits/8);
// Initialize Matrix//
matrix = new(unsigned int[height*width]);
for(int h=height-1;h>=0;h--)
{
for(int w=0;w<=width-1;w++)
{
file.seekg(sof,ios::beg);
file.read(tmp,(int)(ColorBits/8));
tx = BinToNum(tmp,(int)(ColorBits/8));
matrix[(h*width)+w] = tx;
sof+=(int)(ColorBits/8);
}
sof +=pad;
}
}
}
file.close();
return 1;
}
Note:This functions is member of a class that i named it "PIC"...