Sign in to follow this  
Shawn619

OpenGL BMP file problem

Recommended Posts

My opengl program loads BMP's like such:

 

//Makes the image into a texture, and returns the id of the texture
GLuint loadTexture(Image* image) {
GLuint textureId;
glGenTextures(1, &textureId);
 
//Make room for our texture
glBindTexture(GL_TEXTURE_2D, textureId);
 
//Tell OpenGL which texture to edit
 
 
//Map the image to the texture
glTexImage2D(GL_TEXTURE_2D,
 
//Always GL_TEXTURE_2D
0,
 
//0 for now
GL_RGB,
 
//Format OpenGL uses for image
image->width, image->height,
 
//Width and height
0,
 
//The border of the image
GL_RGB,
 
//GL_RGB, because pixels are stored in RGB format
GL_UNSIGNED_BYTE,
 
//GL_UNSIGNED_BYTE, because pixels are stored
 
 
//as unsigned numbers
image->pixels);
 
//The actual pixel data
 
 
return textureId; //Returns the id of the texture
}
 

 

 

with assistance from the imageloader.cpp&.h files:

 

//imageloader.cpp
#include
 
 
<assert.h>
#include
 
 
<fstream>
#include
 
 
"imageloader.h"
using
 
 
namespace std;
Image::Image(
 
char* ps, int w, int h) : pixels(ps), width(w), height(h) {
 
}
Image::~Image() {
 
 
delete[] pixels;
}
namespace
 
 
{
 
 
//Converts a four-character array to an integer, using little-endian form
 
 
int toInt(const char* bytes) {
 
 
return (int)(((unsigned char)bytes[3] << 24) |
((
 
unsigned char)bytes[2] << 16) |
((
 
unsigned char)bytes[1] << 8) |
(
 
unsigned char)bytes[0]);
}
 
 
 
//Converts a two-character array to a short, using little-endian form
 
 
short toShort(const char* bytes) {
 
 
return (short)(((unsigned char)bytes[1] << 8) |
(
 
unsigned char)bytes[0]);
}
 
 
 
//Reads the next four bytes as an integer, using little-endian form
 
 
int readInt(ifstream &input) {
 
 
char buffer[4];
input.read(buffer, 4);
 
 
return toInt(buffer);
}
 
 
 
//Reads the next two bytes as a short, using little-endian form
 
 
short readShort(ifstream &input) {
 
 
char buffer[2];
input.read(buffer, 2);
 
 
return toShort(buffer);
}
 
 
 
//Just like auto_ptr, but for arrays
 
 
template<class T>
 
 
class auto_array {
 
 
private:
T*
 
array;
 
 
mutable bool isReleased;
 
 
public:
 
 
explicit auto_array(T* array_ = NULL) :
 
 
array(array_), isReleased(false) {
}
 
auto_array(
 
const auto_array<T> &aarray) {
 
 
array = aarray.array;
isReleased = aarray.isReleased;
aarray.isReleased =
 
true;
}
 
~auto_array() {
 
 
if (!isReleased && array != NULL) {
 
 
delete[] array;
}
}
 
T* get()
 
const {
 
 
return array;
}
 
T &
 
operator*() const {
 
 
return *array;
}
 
 
 
void operator=(const auto_array<T> &aarray) {
 
 
if (!isReleased && array != NULL) {
 
 
delete[] array;
}
 
 
array = aarray.array;
isReleased = aarray.isReleased;
aarray.isReleased =
 
true;
}
 
T*
 
operator->() const {
 
 
return array;
}
 
T* release() {
isReleased =
 
true;
 
 
return array;
}
 
 
 
void reset(T* array_ = NULL) {
 
 
if (!isReleased && array != NULL) {
 
 
delete[] array;
}
 
 
array = array_;
}
 
T*
 
operator+(int i) {
 
 
return array + i;
}
 
T &
 
operator[](int i) {
 
 
return array[i];
}
};
}
Image* loadBMP(
 
const char* filename) {
ifstream input;
input.open(filename, ifstream::binary);
assert(!input.fail() || !
 
"Could not find file");
 
 
char buffer[2];
input.read(buffer, 2);
assert(buffer[0] ==
 
'B' && buffer[1] == 'M' || !"Not a bitmap file");
input.ignore(8);
 
 
int dataOffset = readInt(input);
 
 
 
//Read the header
 
 
int headerSize = readInt(input);
 
 
int width;
 
 
int height;
 
 
switch(headerSize) {
 
 
case 40:
 
 
//V3
width = readInt(input);
height = readInt(input);
input.ignore(2);
assert(readShort(input) == 24 || !
 
"Image is not 24 bits per pixel");
assert(readShort(input) == 0 || !
 
"Image is compressed");
 
 
break;
 
 
case 12:
 
 
//OS/2 V1
width = readShort(input);
height = readShort(input);
input.ignore(2);
assert(readShort(input) == 24 || !
 
"Image is not 24 bits per pixel");
 
 
break;
 
 
case 64:
 
 
//OS/2 V2
assert(!
 
"Can't load OS/2 V2 bitmaps");
 
 
break;
 
 
case 108:
 
 
//Windows V4
assert(!
 
"Can't load Windows V4 bitmaps");
 
 
break;
 
 
case 124:
 
 
//Windows V5
assert(!
 
"Can't load Windows V5 bitmaps");
 
 
break;
 
 
default:
assert(!
 
"Unknown bitmap format");
}
 
 
 
//Read the data
 
 
int bytesPerRow = ((width * 3 + 3) / 4) * 4 - (width * 3 % 4);
 
 
int size = bytesPerRow * height;
auto_array<
 
char> pixels(new char[size]);
input.seekg(dataOffset, ios_base::beg);
input.read(pixels.get(), size);
 
 
 
//Get the data into the right format
auto_array<
 
char> pixels2(new char[width * height * 3]);
 
 
for(int y = 0; y < height; y++) {
 
 
for(int x = 0; x < width; x++) {
 
 
for(int c = 0; c < 3; c++) {
pixels2[3 * (width * y + x) + c] =
pixels[bytesPerRow * y + 3 * x + (2 - c)];
}
}
}
 
input.close();
 
 
return new Image(pixels2.release(), width, height);
}
?
?
?
?
?
?
?
?
?

 

 

//imageloader.h
#ifndef
 
 
IMAGE_LOADER_H_INCLUDED
#define
 
 
IMAGE_LOADER_H_INCLUDED
//Represents an image
class
 
 
Image {
 
 
public:
Image(
 
char* ps, int w, int h);
~Image();
 
 
 
/* An array of the form (R1, G1, B1, R2, G2, B2, ...) indicating the
* color of each pixel in image. Color components range from 0 to 255.
* The array starts the bottom-left pixel, then moves right to the end
* of the row, then moves up to the next column, and so on. This is the
* format in which OpenGL likes images.
*/
 
 
char* pixels;
 
 
int width;
 
 
int height;
};
//Reads a bitmap image from file.
Image* loadBMP(
 
const char* filename);
#endif

 

 

I get the error: "Can't load windows V4 bitmaps" when i load this image:

j74u8o.jpg

 

But it works PERFECTLY when i load this image->

wvsxvq.jpg

 

 

Why can't i load the 1st image? Both images are 256x256, 24bit and BMP files.

Share this post


Link to post
Share on other sites

there are multiple .bmp formats, and your first image is a funky microsoft one, whereas the second one is a standard 24 bpp bitmap... this is what you can expect from extracting random images from random places.. open the first one in an image editing program (that is NOT Windows Paint) and re-save it as a standard 24-bit bitmap (that means no RLE or anything else funky)... your image loading code relies on the bitmap being stored as essentially raw pixel data.

Share this post


Link to post
Share on other sites

@Brother Bob, i can see the error is because "headersize==108", but i know nothing about the structure of .BMP files.

 

@radioteeth, i tried to save the first image through Gimp 2.0->export->windows BMP->24 bitmap, but with no luck.

Share this post


Link to post
Share on other sites

did you check 'do not write colorspace information' in the compatibility options dropdown while exporting?  it falls under the "anything else funky" category I mentioned above.

 

edit: to clarify, writing colorspace information is funky, so make sure it's checked this time.

Edited by radioteeth

Share this post


Link to post
Share on other sites

The problem with other image loading libraries is they hard to setup and often never have a clear tutorial on how to use them. I tried to setup DevIL a few days ago and multiple problems occured.

Share this post


Link to post
Share on other sites

What's a more productive use of your time: learning to use a library that can effortlessly load and save images in (for all intents and purposes) any format you desire or trying to fix tedious problems in a custom BMP loader? DevIL can even do the heavy lifting for OpenGL texture creation for you.

 

http://openil.sourceforge.net/tuts/tut_1/index.htm

Share this post


Link to post
Share on other sites

I made two bitmaps in gimp, one with colorspace information, one without, opened them up in a hex editor, found the byte your code does the switch/case statement on, with colorspace info included the value is 108, without it the value is 40, which is what your code relies on in order to operate. Therefore, either your GIMP version is broken (ignoring the checkbox?) or you're missing something..

 

On a personal note, this is why I study all file formats and write my own loading code from scratch. I avoid jpeg format because there are seemingly endless variants. Your code looks like it should work just fine with the bitmaps output by GIMP.

 

If you're getting the SAME windows v4 error, then you are obviously not replacing the actual bitmap file that your program is trying to load.

Share this post


Link to post
Share on other sites
I made two bitmaps in gimp, one with colorspace information, one without, opened them up in a hex editor, found the byte your code does the switch/case statement on, with colorspace info included the value is 108, without it the value is 40, which is what your code relies on in order to operate. Therefore, either your GIMP version is broken (ignoring the checkbox?) or you're missing something..

 

On a personal note, this is why I study all file formats and write my own loading code from scratch. I avoid jpeg format because there are seemingly endless variants. Your code looks like it should work just fine with the bitmaps output by GIMP.

 

If you're getting the SAME windows v4 error, then you are obviously not replacing the actual bitmap file that your program is trying to load.

Hey Radio, you're completely right and i appreciate you going the extra step for me. It loads perfectly now. Apparently exporting over the same file does not write over it. What i  should have done was use GIMP's "overwrite" function, which didn't exist years ago when i used GIMP. Thanks Radio :)

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  

  • Announcements

  • Forum Statistics

    • Total Topics
      628333
    • Total Posts
      2982139
  • Similar Content

    • By DejayHextrix
      Hi, New here. 
      I need some help. My fiance and I like to play this mobile game online that goes by real time. Her and I are always working but when we have free time we like to play this game. We don't always got time throughout the day to Queue Buildings, troops, Upgrades....etc.... 
      I was told to look into DLL Injection and OpenGL/DirectX Hooking. Is this true? Is this what I need to learn? 
      How do I read the Android files, or modify the files, or get the in-game tags/variables for the game I want? 
      Any assistance on this would be most appreciated. I been everywhere and seems no one knows or is to lazy to help me out. It would be nice to have assistance for once. I don't know what I need to learn. 
      So links of topics I need to learn within the comment section would be SOOOOO.....Helpful. Anything to just get me started. 
      Thanks, 
      Dejay Hextrix 
    • By mellinoe
      Hi all,
      First time poster here, although I've been reading posts here for quite a while. This place has been invaluable for learning graphics programming -- thanks for a great resource!
      Right now, I'm working on a graphics abstraction layer for .NET which supports D3D11, Vulkan, and OpenGL at the moment. I have implemented most of my planned features already, and things are working well. Some remaining features that I am planning are Compute Shaders, and some flavor of read-write shader resources. At the moment, my shaders can just get simple read-only access to a uniform (or constant) buffer, a texture, or a sampler. Unfortunately, I'm having a tough time grasping the distinctions between all of the different kinds of read-write resources that are available. In D3D alone, there seem to be 5 or 6 different kinds of resources with similar but different characteristics. On top of that, I get the impression that some of them are more or less "obsoleted" by the newer kinds, and don't have much of a place in modern code. There seem to be a few pivots:
      The data source/destination (buffer or texture) Read-write or read-only Structured or unstructured (?) Ordered vs unordered (?) These are just my observations based on a lot of MSDN and OpenGL doc reading. For my library, I'm not interested in exposing every possibility to the user -- just trying to find a good "middle-ground" that can be represented cleanly across API's which is good enough for common scenarios.
      Can anyone give a sort of "overview" of the different options, and perhaps compare/contrast the concepts between Direct3D, OpenGL, and Vulkan? I'd also be very interested in hearing how other folks have abstracted these concepts in their libraries.
    • By aejt
      I recently started getting into graphics programming (2nd try, first try was many years ago) and I'm working on a 3d rendering engine which I hope to be able to make a 3D game with sooner or later. I have plenty of C++ experience, but not a lot when it comes to graphics, and while it's definitely going much better this time, I'm having trouble figuring out how assets are usually handled by engines.
      I'm not having trouble with handling the GPU resources, but more so with how the resources should be defined and used in the system (materials, models, etc).
      This is my plan now, I've implemented most of it except for the XML parts and factories and those are the ones I'm not sure of at all:
      I have these classes:
      For GPU resources:
      Geometry: holds and manages everything needed to render a geometry: VAO, VBO, EBO. Texture: holds and manages a texture which is loaded into the GPU. Shader: holds and manages a shader which is loaded into the GPU. For assets relying on GPU resources:
      Material: holds a shader resource, multiple texture resources, as well as uniform settings. Mesh: holds a geometry and a material. Model: holds multiple meshes, possibly in a tree structure to more easily support skinning later on? For handling GPU resources:
      ResourceCache<T>: T can be any resource loaded into the GPU. It owns these resources and only hands out handles to them on request (currently string identifiers are used when requesting handles, but all resources are stored in a vector and each handle only contains resource's index in that vector) Resource<T>: The handles given out from ResourceCache. The handles are reference counted and to get the underlying resource you simply deference like with pointers (*handle).  
      And my plan is to define everything into these XML documents to abstract away files:
      Resources.xml for ref-counted GPU resources (geometry, shaders, textures) Resources are assigned names/ids and resource files, and possibly some attributes (what vertex attributes does this geometry have? what vertex attributes does this shader expect? what uniforms does this shader use? and so on) Are reference counted using ResourceCache<T> Assets.xml for assets using the GPU resources (materials, meshes, models) Assets are not reference counted, but they hold handles to ref-counted resources. References the resources defined in Resources.xml by names/ids. The XMLs are loaded into some structure in memory which is then used for loading the resources/assets using factory classes:
      Factory classes for resources:
      For example, a texture factory could contain the texture definitions from the XML containing data about textures in the game, as well as a cache containing all loaded textures. This means it has mappings from each name/id to a file and when asked to load a texture with a name/id, it can look up its path and use a "BinaryLoader" to either load the file and create the resource directly, or asynchronously load the file's data into a queue which then can be read from later to create the resources synchronously in the GL context. These factories only return handles.
      Factory classes for assets:
      Much like for resources, these classes contain the definitions for the assets they can load. For example, with the definition the MaterialFactory will know which shader, textures and possibly uniform a certain material has, and with the help of TextureFactory and ShaderFactory, it can retrieve handles to the resources it needs (Shader + Textures), setup itself from XML data (uniform values), and return a created instance of requested material. These factories return actual instances, not handles (but the instances contain handles).
       
       
      Is this a good or commonly used approach? Is this going to bite me in the ass later on? Are there other more preferable approaches? Is this outside of the scope of a 3d renderer and should be on the engine side? I'd love to receive and kind of advice or suggestions!
      Thanks!
    • By nedondev
      I 'm learning how to create game by using opengl with c/c++ coding, so here is my fist game. In video description also have game contain in Dropbox. May be I will make it better in future.
      Thanks.
    • By Abecederia
      So I've recently started learning some GLSL and now I'm toying with a POM shader. I'm trying to optimize it and notice that it starts having issues at high texture sizes, especially with self-shadowing.
      Now I know POM is expensive either way, but would pulling the heightmap out of the normalmap alpha channel and in it's own 8bit texture make doing all those dozens of texture fetches more cheap? Or is everything in the cache aligned to 32bit anyway? I haven't implemented texture compression yet, I think that would help? But regardless, should there be a performance boost from decoupling the heightmap? I could also keep it in a lower resolution than the normalmap if that would improve performance.
      Any help is much appreciated, please keep in mind I'm somewhat of a newbie. Thanks!
  • Popular Now