OpenGL纹理格式的颜色错误

Question

我尝试使用FreeImage加载图像，然后生成OpenGL纹理。它加载图像并生成纹理，但颜色存在问题。

这是原始图片：

并且结果如下：

纹理加载代码：

void TextureManager::LoadTexture(std::string id, std::string filePath){

Texture tex;
tex.TextureId = 0;

FIBITMAP* image = FreeImage_Load(FreeImage_GetFileType(filePath.c_str(), 0), filePath.c_str());


if (FreeImage_GetBPP(image) != 32) {

    image = FreeImage_ConvertTo32Bits(image);
}


FreeImage_FlipVertical(image);

tex.Width = FreeImage_GetWidth(image);
tex.Height = FreeImage_GetHeight(image);


glGenTextures(1, &tex.TextureId);
glBindTexture(GL_TEXTURE_2D, tex.TextureId);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);


glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,tex.Width, tex.Height, 0, GL_RGBA, GL_UNSIGNED_BYTE, (void*)FreeImage_GetBits(image));

AddTextureToMap(id, tex);

FreeImage_Unload(image);
}

以下是绘制它的代码：

glEnable(GL_TEXTURE_2D);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glBindTexture(GL_TEXTURE_2D, TextureManager.TextureMap[textureSelector].TextureId);

glBegin(GL_TRIANGLES);
glTexCoord2d(0, 0);
glVertex3f(-0.75, 0.75, 0);//top left
glTexCoord2d(1, 0);
glVertex3f(0.75, 0.75, 0);//top right
glTexCoord2d(0, 1);
glVertex3f(-0.75, -0.75, 0);//bottom left

glTexCoord2d(1, 0);
glVertex3f(0.75, 0.75, 0);//top right
glTexCoord2d(1, 1);
glVertex3f(0.75, -0.75, 0);//bottom right
glTexCoord2d(0, 1);
glVertex3f(-0.75, -0.75, 0);//bottom left
glEnd();
glFinish();

我很确定glTexImage2D中的内部格式存在问题，但我不知道如果是这种情况我会使用哪种格式。我的问题是：它是格式，如果是，我应该使用什么;还是有另一个导致这个问题的问题？

Answer 1

尝试使用此代替

不同之处在于，许多图像格式使用反向字节顺序，您应该使用GL_BGR_EXT或GL_BGRA_EXT图像格式而不是GL_RGB或GL_RGBA

void TextureManager::LoadTexture(std::string id, std::string filePath){

Texture tex;
tex.TextureId = 0;

FIBITMAP* image = FreeImage_Load(FreeImage_GetFileType(filePath.c_str(), 0), filePath.c_str());


if (FreeImage_GetBPP(image) != 32) {

    image = FreeImage_ConvertTo32Bits(image);
}


FreeImage_FlipVertical(image);

tex.Width = FreeImage_GetWidth(image);
tex.Height = FreeImage_GetHeight(image);


glGenTextures(1, &tex.TextureId);
glBindTexture(GL_TEXTURE_2D, tex.TextureId);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);


glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,tex.Width, tex.Height, 0, GL_BGRA_EXT, GL_UNSIGNED_BYTE, (void*)FreeImage_GetBits(image));

AddTextureToMap(id, tex);

FreeImage_Unload(image);
}

Answer 2

如果RGBA顺序不正确，则可以在片段着色器中更改颜色，例如

#version 130

uniform sampler2D tex;

in vec2 texCoordsVarying;
out vec4 color;

void main() {
  vec4 c2 = texture(tex, texCoordsVarying);
  color = vec4(c2.g, c2.b, c2.a, c2.r);
}