iOS - pass UIImage to shader as texture - ios

Question

I am trying to pass UIImage to GLSL shader. The fragment shader is:
varying highp vec2 textureCoordinate;
uniform sampler2D inputImageTexture;
uniform sampler2D inputImageTexture2;
void main()
{
highp vec4 color = texture2D(inputImageTexture, textureCoordinate);
highp vec4 color2 = texture2D(inputImageTexture2, textureCoordinate);
gl_FragColor = color * color2;
}
What I want to do is send images from camera and do multiply blend with texture. When I just send data from camera, everything is fine. So problem should be with sending another texture to shader. I am doing it this way:
- (void)setTexture:(UIImage*)image forUniform:(NSString*)uniform {
CGSize sizeOfImage = [image size];
CGFloat scaleOfImage = [image scale];
CGSize pixelSizeOfImage = CGSizeMake(scaleOfImage * sizeOfImage.width, scaleOfImage * sizeOfImage.height);
//create context
GLubyte * spriteData = (GLubyte *)malloc(pixelSizeOfImage.width * pixelSizeOfImage.height * 4 * sizeof(GLubyte));
CGContextRef spriteContext = CGBitmapContextCreate(spriteData, pixelSizeOfImage.width, pixelSizeOfImage.height, 8, pixelSizeOfImage.width * 4, CGImageGetColorSpace(image.CGImage), kCGImageAlphaPremultipliedLast);
//draw image into context
CGContextDrawImage(spriteContext, CGRectMake(0.0, 0.0, pixelSizeOfImage.width, pixelSizeOfImage.height), image.CGImage);
//get uniform of texture
GLuint uniformIndex = glGetUniformLocation(__programPointer, [uniform UTF8String]);
//generate texture
GLuint textureIndex;
glGenTextures(1, &textureIndex);
glBindTexture(GL_TEXTURE_2D, textureIndex);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
//create texture
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, pixelSizeOfImage.width, pixelSizeOfImage.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, textureIndex);
//"send" to shader
glUniform1i(uniformIndex, 1);
free(spriteData);
CGContextRelease(spriteContext);
}
Uniform for texture is fine, glGetUniformLocation function do not returns -1. The texture is PNG file of resolution 2000x2000 pixels.
PROBLEM: When the texture is passed to shader, I have got "black screen". Maybe problem are parameters of the CGContext or parameters of the function glTexImage2D
UPDATE: I have just found out I need to pass texture unit number to uniform every draw cycle and everything works just fine. It is really necessary to do it?
Thank you