• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
thecoast47

reading 24 bit per pixel bitmaps issue

7 posts in this topic

I'm currently trying to read bitmaps without using an image library.

My current implementation can read bitmaps ,however, issues occur when both the width and height are not of base 2. 

To be more specific, when I tired to render a 922x910 bitmap ,the colors didn't come in correctly. Sometimes bitmaps of different resolutions turnout looking "stretched" and without the correct colors.  

To get my bitmaps I let microsoft paint convert png's, jpegs and other formats to .bmp.

The ultimate purpose for all of this is to implement the marching squares method so I can generate polygons from sprites.

How do I deal with this? 

 

My bitmap code so far:

#ifndef COLOR_VECTOR
#define COLOR_VECTOR
struct ColorVector{
    unsigned char r;
    unsigned char g;
    unsigned char b;
    unsigned char a;
};
#endif

 

class uBitmap{
    public:
        uBitmap(std::string path,BYTE redColorKey, BYTE greenColorKey,BYTE blueColorKey);
        ~uBitmap();
        unsigned int getWidth();
        unsigned int getHeight();
        long int getPixel(int x, int y);
        ColorVector getPixelVector(int x, int y);
        void resizeBuffer(unsigned int size);
        void clearBuffer();
        void putPixel(int x, int y, BYTE r, BYTE g, BYTE b);
        void saveBitmap(std::string filename);
        void renderImage();
    private:
        BITMAPFILEHEADER bitmapHeader_;
        BITMAPINFOHEADER bitmapInfoHeader_;
        BYTE* rgbPixelData_;
        BYTE* rgbaPixelData_;
        ColorVector colorKey_;
};

 

 

uBitmap::uBitmap(std::string path,BYTE redColorKey, BYTE greenColorKey,BYTE blueColorKey){
    BITMAPFILEHEADER& fileHeader = bitmapHeader_;
    BITMAPINFOHEADER& infoHeader = bitmapInfoHeader_;
    BYTE*& pixelData = rgbPixelData_;

    bitmapInfoHeader_.biWidth = 0;
    bitmapInfoHeader_.biHeight = 0;
    rgbPixelData_ = NULL;
    rgbaPixelData_ = NULL;

    std::ifstream file(path.data(),std::ios::binary);
    if(file.is_open()){
        file.read((char*)&bitmapHeader_    ,sizeof(BITMAPFILEHEADER));
        file.read((char*)&bitmapInfoHeader_,sizeof(BITMAPINFOHEADER));
        rgbPixelData_ = new BYTE[infoHeader.biSizeImage];
        file.read((char*)rgbPixelData_,infoHeader.biSizeImage);
    }
    file.close();
}

uBitmap::~uBitmap(){
    if(rgbPixelData_ != NULL){
        delete[] rgbPixelData_;
    }

    if(rgbaPixelData_ != NULL){
        delete[] rgbaPixelData_;
    }
}

unsigned int uBitmap::getWidth(){
    return bitmapInfoHeader_.biWidth;
}

unsigned int uBitmap::getHeight(){
    return bitmapInfoHeader_.biHeight;
}

/*long int uBitmap::getPixel(int x, int y){// attempting to pack color components into an integer
    ColorVector pix = getPixelVector(x,y);
    return  (pix.b << 24) | (pix.g << 16)  | (pix.r << 8) ;
}*/

ColorVector uBitmap::getPixelVector(int x, int y){
    ColorVector curElement;
    unsigned int firstComponent = (y*getWidth()+x)*3;//which is the blue color vector component
    curElement.b = *(rgbPixelData_+firstComponent);  //reading first component (blue)
    curElement.g = *(rgbPixelData_+firstComponent+1);//reading second component (green)
    curElement.r = *(rgbPixelData_+firstComponent+2);//reading third component (red)
    return curElement;
}

void uBitmap::renderImage(){
    glBegin(GL_POINTS);
    for(unsigned int y = 0; y < getHeight();y++){
        for(unsigned int x = 0; x < getWidth();x++){
            ColorVector c = getPixelVector(x,getHeight() - y);
            glColor3ub(c.r,c.g ,c.b);
            glVertex2i(x,y);
        }
    }
    glEnd();
}

Please note:I realize that using immediate mode to render a bitmap is a horrible idea,however, its more a debugging function than anything else. Just putting that out there. 

 

*EDIT*

I seemed to have fixed the problem. You guys were completely right about the padding. All I did was slightly modify the constructor to fix my problem:

uBitmap::uBitmap(std::string path,BYTE redColorKey, BYTE greenColorKey,BYTE blueColorKey{
    BITMAPFILEHEADER& fileHeader = bitmapHeader_;
    BITMAPINFOHEADER& infoHeader = bitmapInfoHeader_;
    BYTE*& pixelData = rgbPixelData_;
    bitmapInfoHeader_.biWidth = 0;
    bitmapInfoHeader_.biHeight = 0;
    rgbPixelData_ = NULL;
    rgbaPixelData_ = NULL;

    std::ifstream file(path.data(),std::ios::binary);
    if(file.is_open()){
        file.read((char*)&bitmapHeader_    ,sizeof(BITMAPFILEHEADER));
        file.read((char*)&bitmapInfoHeader_,sizeof(BITMAPINFOHEADER));
        
        int desiredRow = int(ceilf((((float)getWidth())*3.0f) / 4.0f) * 4.0f);
        int rowPadding = desiredRow - (getWidth()*3);
        rgbPixelData_ = new BYTE[ (getWidth()*getHeight()*3) + (rowPadding*getHeight());
        for(unsigned int I = 0; I < getHeight();I++){
            file.read(((char*)rgbPixelData_)+(I*getWidth()*3),desiredRow);
        }

    }
    file.close();
}
Edited by thecoast47
0

Share this post


Link to post
Share on other sites
I don't know the details of the bmp format, but you may want to check to see if it employs a stride in non-pow2 images, which would effect the offset of texels within the data. 'Stride' is essentially used for handling a 'padding' space at the end of each row which aligns the data to the next nearest pow2. The stride value should be either the width of the padding or else the width of a row with the padding included.

Can you post an image showing the kind of distortion you're getting? Edited by Khatharr
1

Share this post


Link to post
Share on other sites
I don't know the details of the bmp format, but you may want to check to see if it employs a stride in non-pow2 images, which would effect the offset of texels within the data. 'Stride' is essentially used for handling a 'padding' space at the end of each row which aligns the data to the next nearest pow2. The stride value should be either the width of the padding or else the width of a row with the padding included.

Can you post an image showing the kind of distortion you're getting?

This is what I get when i try to render a 305x298 bitmap 

0

Share this post


Link to post
Share on other sites
Bitmap images do have a padding. Every row of pixel data must be padded to a full multiple of 32 bit.<br /><br />So for your example, with 305 pixels, 305 * 3 (24bit) = 915 bytes per row. The next full multiple is at 916, so you have to read one extra padding byte.
2

Share this post


Link to post
Share on other sites

I remember struggling with this a few years ago. I wrote a class and demo that demonstrate specifically rendering to bitmaps. I think you will find the source code helpful for understanding bitmaps better.

 

Note that while the class supports working with 24-bit bitmaps, you will find the performance when working with 32-bit bitmaps much better.

Find the demo and blog post here: http://code-section.com/entry/20/gdi-memory-bitmap

I hope this helps.

0

Share this post


Link to post
Share on other sites
Once a few years ago I wanted to write bmp load and safe routines too. What I found out was that the format is a badly documented, actually 5+ different incompatible formats with one file extension and if you pick one to write your data out you depend on the mercy and undocumented quirks of the loading routine of some other program you try to get your data into, to support this exact format and actually recognize the version you used and reads all headerfields exactly in the way you wrote them out and not just ignore some and read data at some offset itself always uses for writing.
You better just get some tested image library that can handle better file formats like for example png than rolling your own quirky bmp loader that works on some files but silently garbles others. Or if you really want to load a bmp at least use some Windows function so you can have halfway compatible quirks in your loading routine. Edited by wintertime
2

Share this post


Link to post
Share on other sites
...snip...

Yeah, BMP is a bad format to use. Bloated, poorly documented, difficult to load, etc. I prefer TGA. There is tons of information on the format, it is easy to load and not protected by patents like PNG.
0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0