I am starting to use ImageMagick and the MagickWand API in a simple C program.
Right now, as a test, I am just looking for black pixels in a frame.
Here is my code :
int find_black_pixel(MagickWand *wand) {
int res = 0;
PixelIterator * iterator = NewPixelIterator(wand);
size_t width=MagickGetImageWidth(wand);
size_t height=MagickGetImageHeight(wand);
PixelWand ** pixels;
unsigned long x,y;
unsigned int alpha;
unsigned int red, green, blue;
//printf("Width : %d, Height : %d\n", (int)width, (int)height);
for (y=0; y<height; y++) {
pixels = PixelGetNextIteratorRow(iterator, &width);
for (x=0; x<width; x++) {
alpha = (unsigned int) (255*PixelGetAlpha(pixels[x]));
if (alpha == 0)
continue;
red = (unsigned int) (255*PixelGetRed(pixels[x]));
green = (unsigned int) (255*PixelGetGreen(pixels[x]));
blue = (unsigned int) (255*PixelGetBlue(pixels[x]));
//printf("At %04ld,%04ld, alpha : %d, rgb : %d,%d,%d\n", x,y,alpha, red, green, blue);
if ((red ==0) || (green == 0) || (blue ==0)) {
res = 1;
//DestroyPixelWands(pixels, width);
goto finished_find_black_pixel;
}
}
//DestroyPixelWands(pixels, (size_t)width);
}
finished_find_black_pixel:
DestroyPixelIterator(iterator);
return res;
}
If I uncomment any of the DestroyPixelWands call, I get an assertion :
test: wand/pixel-wand.c:283: DestroyPixelWands: Assertion `(*wand)->signature == 0xabacadabUL' failed.
Any idea why this is happening ?
EDIT :
More debugging... Even calling DestroyPixelWand(pixels[0]); makes it fail the same way...
I suspect that pixels is not a separate destroyable object (it is just a pointer into the original wand object) and that your current code is fine without any code to destroy pixels.
Got the answer from ImageMagick forum :
The pixel wands are private when associated with a pixel iterator. The
pixel wands are destroyed when you destroy the pixel iterator. Do not
use DestroyPixelWands() for a pixel iterator.
Related
I'm building a small program to capture the screen (using X11 MIT-SHM extension) on video. It works well if I create individual PNG files of the captured frames, but now I'm trying to integrate libav (ffmpeg) to create the video and I'm getting... funny results.
The furthest I've been able to reach is this. The expected result (which is a PNG created directly from the RGB data of the XImage file) is this:
However, the result I'm getting is this:
As you can see the colors are funky and the image appears cropped three times. I have a loop where I capture the screen, and first I generate the individual PNG files (currently commented in the code below) and then I try to use libswscale to convert from RGB24 to YUV420:
while (gRunning) {
printf("Processing frame framecnt=%i \n", framecnt);
if (!XShmGetImage(display, RootWindow(display, DefaultScreen(display)), img, 0, 0, AllPlanes)) {
printf("\n Ooops.. Something is wrong.");
break;
}
// PNG generation
// snprintf(imageName, sizeof(imageName), "salida_%i.png", framecnt);
// writePngForImage(img, width, height, imageName);
unsigned long red_mask = img->red_mask;
unsigned long green_mask = img->green_mask;
unsigned long blue_mask = img->blue_mask;
// Write image data
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
unsigned long pixel = XGetPixel(img, x, y);
unsigned char blue = pixel & blue_mask;
unsigned char green = (pixel & green_mask) >> 8;
unsigned char red = (pixel & red_mask) >> 16;
pixel_rgb_data[y * width + x * 3] = red;
pixel_rgb_data[y * width + x * 3 + 1] = green;
pixel_rgb_data[y * width + x * 3 + 2] = blue;
}
}
uint8_t* inData[1] = { pixel_rgb_data };
int inLinesize[1] = { in_w };
printf("Scaling frame... \n");
int sliceHeight = sws_scale(sws_context, inData, inLinesize, 0, height, pFrame->data, pFrame->linesize);
printf("Obtained slice height: %i \n", sliceHeight);
pFrame->pts = framecnt * (pVideoStream->time_base.den) / ((pVideoStream->time_base.num) * 25);
printf("Frame pts: %li \n", pFrame->pts);
int got_picture = 0;
printf("Encoding frame... \n");
int ret = avcodec_encode_video2(pCodecCtx, &pkt, pFrame, &got_picture);
// int ret = avcodec_send_frame(pCodecCtx, pFrame);
if (ret != 0) {
printf("Failed to encode! Error: %i\n", ret);
return -1;
}
printf("Succeed to encode frame: %5d - size: %5d\n", framecnt, pkt.size);
framecnt++;
pkt.stream_index = pVideoStream->index;
ret = av_write_frame(pFormatCtx, &pkt);
if (ret != 0) {
printf("Error writing frame! Error: %framecnt \n", ret);
return -1;
}
av_packet_unref(&pkt);
}
I've placed the entire code at this gist. This question right here looks pretty similar to mine, but not quite, and the solution did not work for me, although I think this has something to do with the way the line stride is calculated.
Don't use av_image_alloc use av_frame_get_buffer.
(unrelated to your question, But using avcodec_encode_video2 is considered bad practice now and should be replaced with avcodec_send_frame and avcodec_receive_packet)
In the end, the error was not in the usage of libav but on the code that fills the pixel data from XImage to the rgb vector. Instead of using:
pixel_rgb_data[y * width + x * 3 ] = red;
pixel_rgb_data[y * width + x * 3 + 1] = green;
pixel_rgb_data[y * width + x * 3 + 2] = blue;
I should have used this:
pixel_rgb_data[3 * (y * width + x) ] = red;
pixel_rgb_data[3 * (y * width + x) + 1] = green;
pixel_rgb_data[3 * (y * width + x) + 2] = blue;
Somehow I was multiplying only the the horizontal displacement within the matrix, not the vertical displacement. The moment I changed it, it worked perfectly.
I'm trying to backport someones Direct3d9 port of Quake 1 by ID software to Direct3d8 so I can port it to the original Xbox (only uses the D3D8 API).
After making the changes to use Direct3d8 it displays some mashed up pixels on the screen that appear to be in little squares :/ (see pictures).
Does anyone know whats gone wrong here? It works flawlessly with D3D9, is there some extra arguments required that I'm missing require for D3D8, rect pitch maybe?
The data been passed in is a Quake 1 .lmp 2d image file. "It consists of two integers (width and height) followed by a string of width x height bytes, each of which is an index into the Quake palette"
Its been passed to the D3D_ResampleTexture() function.
Any help would be much appreciated.
Image output using D3D8
Image output using D3D9
The code:
void D3D_ResampleTexture (image_t *src, image_t *dst)
{
int y, x , srcpos, srcbase, dstpos;
unsigned int *dstdata, *srcdata;
// take an unsigned pointer to the dest data that we'll actually fill
dstdata = (unsigned int *) dst->data;
// easier access to src data for 32 bit resampling
srcdata = (unsigned int *) src->data;
// nearest neighbour for now
for (y = 0, dstpos = 0; y < dst->height; y++)
{
srcbase = (y * src->height / dst->height) * src->width;
for (x = 0; x < dst->width; x++, dstpos++)
{
srcpos = srcbase + (x * src->width / dst->width);
if (src->flags & IMAGE_32BIT)
dstdata[dstpos] = srcdata[srcpos];
else if (src->palette)
dstdata[dstpos] = src->palette[src->data[srcpos]];
else Sys_Error ("D3D_ResampleTexture: !(flags & IMAGE_32BIT) without palette set");
}
}
}
void D3D_LoadTextureStage3 (LPDIRECT3DTEXTURE8/*9*/ *tex, image_t *image)
{
int i;
image_t scaled;
D3DLOCKED_RECT LockRect;
memset (&LockRect, 0, sizeof(D3DLOCKED_RECT));
// check scaling here first
for (scaled.width = 1; scaled.width < image->width; scaled.width *= 2);
for (scaled.height = 1; scaled.height < image->height; scaled.height *= 2);
// clamp to max texture size
if (scaled.width > /*d3d_DeviceCaps.MaxTextureWidth*/640) scaled.width = /*d3d_DeviceCaps.MaxTextureWidth*/640;
if (scaled.height > /*d3d_DeviceCaps.MaxTextureHeight*/480) scaled.height = /*d3d_DeviceCaps.MaxTextureHeight*/480;
IDirect3DDevice8/*9*/_CreateTexture(d3d_Device, scaled.width, scaled.height,
(image->flags & IMAGE_MIPMAP) ? 0 : 1,
/*(image->flags & IMAGE_MIPMAP) ? D3DUSAGE_AUTOGENMIPMAP :*/ 0,
(image->flags & IMAGE_ALPHA) ? D3DFMT_A8R8G8B8 : D3DFMT_X8R8G8B8,
D3DPOOL_MANAGED,
tex
);
// lock the texture rectangle
//(*tex)->LockRect (0, &LockRect, NULL, 0);
IDirect3DTexture8/*9*/_LockRect(*tex, 0, &LockRect, NULL, 0);
// fill it in - how we do it depends on the scaling
if (scaled.width == image->width && scaled.height == image->height)
{
// no scaling
for (i = 0; i < (scaled.width * scaled.height); i++)
{
unsigned int p;
// retrieve the correct texel - this will either be direct or a palette lookup
if (image->flags & IMAGE_32BIT)
p = ((unsigned *) image->data)[i];
else if (image->palette)
p = image->palette[image->data[i]];
else Sys_Error ("D3D_LoadTexture: !(flags & IMAGE_32BIT) without palette set");
// store it back
((unsigned *) LockRect.pBits)[i] = p;
}
}
else
{
// save out lockbits in scaled data pointer
scaled.data = (byte *) LockRect.pBits;
// resample data into the texture
D3D_ResampleTexture (image, &scaled);
}
// unlock it
//(*tex)->UnlockRect (0);
IDirect3DTexture8/*9*/_UnlockRect(*tex, 0);
// tell Direct 3D that we're going to be needing to use this managed resource shortly
//FIXME
//(*tex)->PreLoad ();
}
LPDIRECT3DTEXTURE8/*9*/ D3D_LoadTextureStage2 (image_t *image)
{
d3d_texture_t *tex;
// look for a match
// create a new one
tex = (d3d_texture_t *) malloc (sizeof (d3d_texture_t));
// link it in
tex->next = d3d_Textures;
d3d_Textures = tex;
// fill in the struct
tex->LastUsage = 0;
tex->d3d_Texture = NULL;
// copy the image
memcpy (&tex->TexImage, image, sizeof (image_t));
// upload through direct 3d
D3D_LoadTextureStage3 (&tex->d3d_Texture, image);
// return the texture we got
return tex->d3d_Texture;
}
LPDIRECT3DTEXTURE8/*9*/ D3D_LoadTexture (char *identifier, int width, int height, byte *data, /*bool*/qboolean mipmap, /*bool*/qboolean alpha)
{
image_t image;
image.data = data;
image.flags = 0;
image.height = height;
image.width = width;
image.palette = d_8to24table;
strcpy (image.identifier, identifier);
if (mipmap) image.flags |= IMAGE_MIPMAP;
if (alpha) image.flags |= IMAGE_ALPHA;
return D3D_LoadTextureStage2 (&image);
}
When you lock the texture, you have to observe the returned Pitch member of the D3DLOCKED_RECT structure. Your code is assuming that all the data is contiguous, but the Pitch can be larger than the width of a scanline in order to allow for locking a subregion and other layouts of the buffer that don't have contiguous pixels at the end of one scanline to the beginning of the next.
Look at Chapter 4 of my book "The Direct3D Graphics Pipeline" to see an example of accessing a surface and using the Pitch properly.
For anyone else that comes across this issue, it was due to the way the image was been loaded into the Xbox's memory, it needed to be swizzled.
I want to extract gif frames to raw BGRA data, I used giflib to parse format. I've got first frame (I suppose it's like a key frame in video) that looks good and second (it's 15 frames actually, but let's simplify it) that looks like diff frame. Here is samples:
It seems to be simple to restore second full frame using diff data, but here is the problem: I have no idea what color index means "Not changed". Black pixels on diff frame is actually black – its index in color map is 255, which is rgb(0,0,0). I printed whole color table and didn't found any other black entries. It's here if interested. "BackgroundColor" index is 193, so it makes no sense either.
So, I can't separate "black" color from "no" color. What if second frame will really contain some new black pixels (it contains indeed because left eye moves on animation)? But program should handles it differently: get previous frame color for "no" color and get rgb(0,0,0) for "black" color.
UPD: here is my code. Subframes handling and memory cleanup is ommited. Here I supposed that "no" color index is last in colortable. It works actually for my test file, but I'm not sure it will work in general.
DGifSlurp(image);
int* master = malloc(image->SWidth * image->SHeight * sizeof(int));
for (int i = 0; i < image->ImageCount; i++) {
SavedImage* frame = &image->SavedImages[i];
ColorMapObject* cmap = frame->ImageDesc.ColorMap ? frame->ImageDesc.ColorMap : image->SColorMap;
int nocoloridx = cmap->ColorCount - 1;
IplImage* mat = cvCreateImage(cvSize(frame->ImageDesc.Width, frame->ImageDesc.Height), IPL_DEPTH_8U, 4);
mat->imageData = malloc(frame->ImageDesc.Width * frame->ImageDesc.Height * 4);
for (int y = 0; y < frame->ImageDesc.Height; y++)
for (int x = 0; x < frame->ImageDesc.Width; x++) {
int offset = y * frame->ImageDesc.Width + x;
int coloridx = frame->RasterBits[offset];
if (coloridx == nocoloridx) {
coloridx = master[offset];
} else {
master[offset] = coloridx;
}
GifColorType color = cmap->Colors[coloridx];
cvSetComponent(mat, x, y, 0, color.Blue);
cvSetComponent(mat, x, y, 1, color.Green);
cvSetComponent(mat, x, y, 2, color.Red);
cvSetComponent(mat, x, y, 3, 100);
}
cvNamedWindow("t", CV_WINDOW_AUTOSIZE);
cvShowImage("t", mat);
cvWaitKey(0);
}
void invert( uint8_t array[],
unsigned int cols,
unsigned int rows )
{
int y;
uint8_t darkest = 255;
uint8_t lightest = 0;
uint8_t anygray = y;
for (int x = 0; x < (cols*rows); x++)
{
for (y = 0; y < (cols*rows); y++)
{
if (array[x] == darkest && array[x] == anygray && array[x] == lightest)
{
array[x] = 255-y;
}
}
}
}
I have a function here that inverts the image intensities, so that black becomes white, and vice versa as well as all the light grays become dark grays. But my code here doesn't seem to work and I don't know where i went wrong. Would anybody be able to help me out?
I haven't prototyped anything to check but I see at least two things that look suspicious.
1) I expected the && in the IF to be ||.
2) I expected array[x] = 255 - y to be something like array[x] = 255 - array[x].
I'm trying to use ARtoolkit, but with a static image instead of a video stream. I need to be able to load an image, identify markers, and locate them. I'm using SDL for loading the image. I'm able to obtain the RGB values for each pixel from the loaded image, but I'm unsure how to format the data for ARToolkit to work with it.
ARToolkit stores its images as type ARUint8* (an unsigned char*). I'm confused as to how this format works. Right now I have this code inside the main loop that runs continuously as the program is executing. This code (should) print out the RGB values for each pixel in the frame.
ARUint8* dataPtr;
dataPtr = arVideoGetImage(); // Get a new frame from the webcam
int width, height;
if (arVideoInqSize(&width, &height) == 0) // if width and height could be obtained
{
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
printf("pixel %i, %i: %i, %i, %i\n", x, y, dataPtr[(y * 320) + x], dataPtr[(y * 320) + x + 1], dataPtr[(y * 320) + x + 2]);
}
}
}
Typical output:
pixel 5, 100: 0, 0, 0
pixel 6, 100: 178, 3, 0
pixel 7, 100: 0, 0, 177
etc...
It seems to be accessing the RGB values correctly, but I'm unsure how to copy over the image data (from SDL's format) into this new format.
Figured it out. Posting answer in case anyone else ever needs it.
On Windows, ARToolkit defaults to BGRA for the dataPtr array. The following function will load an image (using SDL) and return a pointer to a ARUint8 (that contains the image data).
ARUint8* loadImage(char* filename, int* w, int* h)
{
SDL_Surface* img = IMG_Load(filename);
if (!img)
{
printf("Image '%s' failed to load. Error: %s\n", filename, IMG_GetError());
return NULL;
}
*w = img->w; // Assign width and height to the given pointers
*h = img->h;
ARUint8* dataPtr = (ARUint8*)calloc(img->w * img->h * 4, sizeof(ARUint8)); // Allocate space for image data
// Write image data to the dataPtr variable
for (int y = 0; y < img->h; y++)
{
for (int x = 0; x < img->w; x++)
{
Uint8 r, g, b;
SDL_GetRGB(getpixel(img, x, y), img->format, &r, &g, &b); // Get the RGB values
int i = ((y * img->w) + x) * 4; // Figure out index in array
dataPtr[i] = b;
dataPtr[i + 1] = g;
dataPtr[i + 2] = r;
dataPtr[i + 3] = 0; // Alpha
}
}
SDL_FreeSurface(img);
return dataPtr;
}
The getpixel function is borrowed from here: http://sdl.beuc.net/sdl.wiki/Pixel_Access
This function allowed me to use a photograph instead of a video feed from a webcam.