i am trying to display an image on iphone by converting it into texture and then displaying it on the UIView.
here is the code to load an image from an UIImage object
- (void)loadImage:(UIImage *)image mipmap:(BOOL)mipmap texture:(uint32_t)texture
{
int width, height;
CGImageRef cgImage;
GLubyte *data;
CGContextRef cgContext;
CGColorSpaceRef colorSpace;
GLenum err;
if (image == nil)
{
NSLog(#"Failed to load");
return;
}
cgImage = [image CGImage];
width = CGImageGetWidth(cgImage);
height = CGImageGetHeight(cgImage);
colorSpace = CGColorSpaceCreateDeviceRGB();
// Malloc may be used instead of calloc if your cg image has dimensions equal to the dimensions of the cg bitmap context
data = (GLubyte *)calloc(width * height * 4, sizeof(GLubyte));
cgContext = CGBitmapContextCreate(data, width, height, 8, width * 4, colorSpace, kCGImageAlphaPremultipliedLast);
if (cgContext != NULL)
{
// Set the blend mode to copy. We don't care about the previous contents.
CGContextSetBlendMode(cgContext, kCGBlendModeCopy);
CGContextDrawImage(cgContext, CGRectMake(0.0f, 0.0f, width, height), cgImage);
glGenTextures(1, &(_textures[texture]));
glBindTexture(GL_TEXTURE_2D, _textures[texture]);
if (mipmap)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
else
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
if (mipmap)
glGenerateMipmapOES(GL_TEXTURE_2D);
err = glGetError();
if (err != GL_NO_ERROR)
NSLog(#"Error uploading texture. glError: 0x%04X", err);
CGContextRelease(cgContext);
}
free(data);
CGColorSpaceRelease(colorSpace);
}
The problem that i currently am facing is this code workd perfectly fine and displays the image on simulator where as on the device as seen on debugger an error is displayed i.e. Error uploading texture. glError: 0x0501
any idea how to tackle this bug....
thnx in advance 4 ur soluitons
If the texture has non-power of two dimensions you need to use EXT_texture_rectangle. (GL_TEXTURE_RECTANGLE_EXT instead of GL_TEXTURE_2D and different texture coordinates).
If that doesn't help it would be good to know which line(s) causes the GL_INVALID_VALUE (0x0501) error.
Related
I am new to iphone development. Currently I am working on a project where opengl is used and I need to animate a part of the view. For that I have taken the screen shot and then created the texture.
This is my code
glEnable(GL_TEXTURE_2D);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_SRC_COLOR);
UIGraphicsBeginImageContext(self.introductionTextLabel.frame.size);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
GLuint texture[1];
glGenTextures(1, &texture[0]);
glBindTexture(GL_TEXTURE_2D, texture[0]);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
GLuint width = CGImageGetWidth(viewImage.CGImage);
GLuint height = CGImageGetHeight(viewImage.CGImage);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
void *imageData = malloc( height * width * 4 );
CGContextRef contextTexture = CGBitmapContextCreate( imageData, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big );
CGColorSpaceRelease( colorSpace );
CGContextClearRect( contextTexture, CGRectMake( 0, 0, width, height ) );
CGContextTranslateCTM( contextTexture, 0, height - height );
CGContextDrawImage( contextTexture, CGRectMake( 0, 0, width, height ), viewImage.CGImage );
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);
CGContextRelease(contextTexture);
free(imageData);
I have searched a lot but could not find a good method for giving an animation for the texture.
Can any one suggest me good method. If I am doing wrong please point out.
Thanks in advance.
The only way I can recommend you to modify the texture is to use glTexImage2D() for full frame update and glTexSubImage2D() for partial update. Of course it will be better if you will use preloaded and compressed type of textures...
I tried to paint a transparent texture over a sphere, but the transparent areas are not completely transparent. A vivid shade of gray remains. I tried to load a Photoshop generated PNG then paint it on sphere using the code below:
My code to load textures:
- (void) loadPNGTexture: (int)index Name: (NSString*) name{
CGImageRef imageRef = [UIImage imageNamed:[NSString stringWithFormat:#"%#.png",name]].CGImage;
GLsizei width = CGImageGetWidth(imageRef);
GLsizei height = CGImageGetHeight(imageRef);
GLubyte * data = malloc(width * 4 * height);
if (!data)
NSLog(#"error allocating memory for texture loading!");
else {
NSLog(#"Memory allocated for %#", name);
}
NSLog(#"Width : %d, Height :%d",width,height);
CGContextRef cg_context = CGBitmapContextCreate(data, width, height, 8, 4 * width, CGImageGetColorSpace(imageRef), kCGImageAlphaPremultipliedLast);//kCGImageAlphaPremultipliedLast);
CGContextTranslateCTM(cg_context, 0, height);
CGContextScaleCTM(cg_context, 1, -1);
CGContextDrawImage(cg_context, CGRectMake(0, 0, width, height), imageRef);
CGContextRelease(cg_context);
CGContextSetBlendMode(cg_context, kCGBlendModeCopy); //kCGBlendModeCopy);
glGenTextures(2, m_texture[index]);
glBindTexture(GL_TEXTURE_2D, m_texture[index][0]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
free(data);
}
Drawing clouds:
glPushMatrix();
glTranslatef(0, 0, 3 );
glScalef(3.1, 3.1, 3.1);
glRotatef(-1, 0, 0, 1);
glRotatef(90, -1, 0, 0);
glDisable(GL_LIGHTING);
//Load Texture for left side of globe
glBindTexture(GL_TEXTURE_2D, m_texture[CLOUD_TEXTURE][0]);
glVertexPointer(3, GL_FLOAT, sizeof(TexturedVertexData3D), &VertexData[0].vertex);
glNormalPointer(GL_FLOAT, sizeof(TexturedVertexData3D), &VertexData[0].normal);
glTexCoordPointer(2, GL_FLOAT, sizeof(TexturedVertexData3D), &VertexData[0].texCoord);
// draw the sphere
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_COPY);
glDrawArrays(GL_TRIANGLES, 0, 11520);
glEnable(GL_LIGHTING);
glPopMatrix();
This first thing that stands out in your code is the line:
glBlendFunc(GL_SRC_ALPHA, GL_COPY);
The second argument (GL_COPY), is not a valid argument for glBlendFunc.
You might want to change that to something along the lines of
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
I've got a nice and short method to load textures in my iPhone app, where I glGenTextures(13, &textures[0]);. Of course at the end of it I do glDeleteTextures(13, textures);, but the memory isn't fully released untill I comment out this line:
CGContextDrawImage(textureContext, CGRectMake(0.0, 0.0, (float)texWidth, (float)texHeight), textureImage);' (which of course results in having the textures totally black) although the next line says:
CGContextRelease(textureContext);
This is the full code for loading the textures:
- (void)loadTexture:(NSString *)name intoLocation:(GLuint)location {
CGImageRef textureImage = [UIImage imageNamed:name].CGImage;
if (textureImage == nil) {
NSLog(#"Failed to load texture image");
return;
}
NSInteger texWidth = CGImageGetWidth(textureImage);
NSInteger texHeight = CGImageGetHeight(textureImage);
GLubyte *textureData = (GLubyte *)malloc(texWidth * texHeight << 2);
int k, l = texWidth * texHeight << 2;
for (k=0; k<l; k++) textureData[k] = 0;
CGContextRef textureContext = CGBitmapContextCreate(textureData, texWidth, texHeight, 8, texWidth << 2, CGImageGetColorSpace(textureImage),
kCGImageAlphaPremultipliedLast);
CGContextTranslateCTM(textureContext, 0, texHeight);
CGContextScaleCTM(textureContext, 1.0, -1.0);
CGContextDrawImage(textureContext, CGRectMake(0.0, 0.0, (float)texWidth, (float)texHeight), textureImage);
CGContextRelease(textureContext);
glBindTexture(GL_TEXTURE_2D, location);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texWidth, texHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, textureData);
free(textureData);
glEnable(GL_TEXTURE_2D);
}
CGImage decodes its data lazily the first time its drawn. It holds on to the decoded data.
The UIImage class caches UIImage instances by name, and the instances hold the CGImages which are holding the decoded data. The UIImage cache is purged in response to low memory warnings.
If this is causing too much memory use in your app, you want to control the creation and destruction of UIImages more carefully, which means not using +[UIImage imageNamed:].
On the other hand, usually an app doesn't have that many named images - it's a static set determined at compile time. If you were just wondering about this memory usage, there you go.
Ok, what I'm trying to achieve is to load an image as a single resource and then save different parts of it as a number of different textures (basically chopping the image into smaller squares and then saving them separately).
For my game, simply mapping different sections of the original image to my shapes won't work and being able to have each 'tile' as a separate texture would be awesome.
Below is the code I'm using for my texture loader. I've tried messing round with the width and height of the texture being loaded but getting some weird results.
Any suggestions would be much appreciated.
Thanks
glBindTexture(GL_TEXTURE_2D, texture[0]);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
NSString *path =
[[NSBundle mainBundle] pathForResource:#"checkerplate" ofType:#"png"];
NSData *texData = [[NSData alloc] initWithContentsOfFile:path];
UIImage *image = [[UIImage alloc] initWithData:texData];
GLuint width = CGImageGetWidth(image.CGImage);
GLuint height = CGImageGetHeight(image.CGImage);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
void *imageData = malloc( height * width * 4 );
CGContextRef context = CGBitmapContextCreate(
imageData, width, height, 8, 4 * width, colorSpace,
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big );
CGColorSpaceRelease( colorSpace );
CGContextClearRect( context, CGRectMake( 0, 0, width, height ) );
CGContextTranslateCTM( context, 0, height - height );
CGContextDrawImage( context, CGRectMake( 0, 0, width, height ), image.CGImage );
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA,
GL_UNSIGNED_BYTE, imageData);
CGContextRelease(context);
free(imageData);
[image release];
[texData release];
Ok, just in case anyone wants to achieve this, i figured it out. All you need to do is modify the line CGContextDrawImage and alter the width and height parameters.
This results in the whole texture being loaded in but then will only draw the area specified on this line.
Basically,
CGContextDrawImage( context, CGRectMake(0, 0, width*2, height*2 ), image.CGImage );
will draw 1/4 of the image (as its height and width are being doubled past the textures size).
:)
I am beginning to work on my first OpenGL iPhone app, but I've hit an early snag.
I have a VERY SIMPLE little texture that I want to use as a sprite in a 2D game, but it renders with weird 'randomly' colored pixels up top.
http://i40.tinypic.com/2s7c9ro.png <-- Screenshot here
I sort of get the feeling that this is Photoshop's fault, so if anybody something about that please let me know.
If it's not photoshop then it's gotta be my code... So here is the code in question...
- (void)loadTexture {
CGImageRef textureImage = [UIImage imageNamed:#"zombie0.png"].CGImage;
if (textureImage == nil) {
NSLog(#"Failed to load texture image");
return;
}
NSInteger texWidth = CGImageGetWidth(textureImage);
NSInteger texHeight = CGImageGetHeight(textureImage);
GLubyte *textureData = (GLubyte *)malloc(texWidth * texHeight * 4);
CGContextRef textureContext = CGBitmapContextCreate(textureData, texWidth, texHeight, 8, texWidth * 4, CGImageGetColorSpace(textureImage), kCGImageAlphaPremultipliedLast);
CGContextDrawImage(textureContext, CGRectMake(0.0, 0.0, (float)texWidth, (float)texHeight), textureImage);
CGContextRelease(textureContext);
glGenTextures(1, &textures[0]);
glBindTexture(GL_TEXTURE_2D, textures[0]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texWidth, texHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, textureData);
free(textureData);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glEnable(GL_TEXTURE_2D);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
}
This blend function yielded the best results.
Please, let me know what you think is wrong.
Thank you very much, this problem has been driving me nuts.
One problem I can see from the code is that you do not clear your context before drawing the image. Since your image contains transparent areas and is composed on the background, you just see what's in the memory allocated by malloc. Try setting you Quartz Blend mode to copy before drawing the image:
CGContextSetBlendMode(textureContext, kCGBlendModeCopy);
You could also use calloc instead of malloc, since calloc gives you zeroed memory.
Your OpenGL blending is correct:
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
gives you Porter-Duff "OVER", which is what you usually want.
Try erasing your CGContextRef first:
CGContextSetRGBFillColor(ctxt, 1, 1, 1, 0);
CGContextFillRect(ctxt, CGRectMake(0, 0, w, h));
Most probably your image has some colored pixels with an zero alpha value, but because of the blending function you are showing them. Try
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);