I searched in INTERNET related to the subject but I found only people that want to save png file with the background transparent.
I report belove the source code that at the moment I use and produces png with background transparent:
cairo_surface_t *surface; // Declarations
cairo_t *cr;
// Creations of the surface
surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32,3508,2480);
// Contest
cr = cairo_create(surface);
// Moving the plot to center in the page
cairo_translate(cr, 200,200);
// Scaling the plot
cairo_scale(cr,1.8,1.8);
// Make all the necessary actions to produce the plot
do_drawing(cr);
// write the plot on the file png
cairo_surface_write_to_png(surface, "image.png");
// End
cairo_surface_destroy(surface);
cairo_destroy(cr);
I used also the surface CAIRO_FORMAT_RGB24 but I obtain a black rectangle like plot.
Please could you help me?
Thank You
cairo_surface_t *surface; // Declarations
cairo_t *cr;
// Creations of the surface
// XXX: Changed to format RGB24; if you don't need transparency, well.
surface = cairo_image_surface_create(CAIRO_FORMAT_RGB24,3508,2480);
// Contest
cr = cairo_create(surface);
// Draw background XXXXXXXXXXXXXXXXXX
cairo_save(cr);
cairo_set_source_rgb(cr, 1, 1, 1);
cairo_paint(cr);
cairo_restore(cr);
// Moving the plot to center in the page
cairo_translate(cr, 200,200);
// Scaling the plot
cairo_scale(cr,1.8,1.8);
// Make all the necessary actions to produce the plot
do_drawing(cr);
// write the plot on the file png
cairo_surface_write_to_png(surface, "image.png");
// End
cairo_surface_destroy(surface);
cairo_destroy(cr);
You need to draw with an opaque background, take a look at the cairo_set_source_rgb function.
Related
I have opened a window which shows two rects on the screen then using SDL_TTF to show the mouse position on the screen.
The bit I am having hard time understanding is why after rendering text the the two rects before it do not show up.
I am using SDL_RenderFillRect to draw two rects on screen
SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
SDL_RenderFillRect(renderer, rect1);
SDL_SetRenderDrawColor(renderer, 0, 0, 255, 255);
SDL_RenderFillRect(renderer, rect2);
Code for rendering the text is
// define string with mouse x, y coords
sprintf(someString, "x: %d, y: %d", mouse.x, mouse.y);
SDL_Point textPos = {10, 10};
WriteText(renderer, font, someString, textPos, (SDL_Color){255, 255, 255, 255});
SDL_Surface *fontSurface = TTF_RenderText_Blended(font, someString, COLOR_BLACK); // create font surface
SDL_Texture *fontTexture = SDL_CreateTextureFromSurface(renderer, fontSurface); // create the texture
// get clip width and height from fontsurface clip rect
SDL_Rect *fontRect = &fontSurface->clip_rect;
fontRect->x = pos.x;
fontRect->y = pos.y;
SDL_RenderCopy(renderer, fontTexture, NULL, fontRect); // copy text to the renderer
// delete surface and texture
SDL_FreeSurface(fontSurface);
SDL_DestroyTexture(fontTexture);
It to shows the mouse positon top left corner of the window. However this makes the rest of the window blank.
To prevent this my work around is having to draw something on the screen after calling SDL_RendererCopy (and weirdly before calling SDL_DestroyTexture too) For example drawing single point
...
SDL_RenderCopy(renderer, fontTexture, NULL, fontRect); // copy text to the renderer
// why is this needed??
SDL_RenderDrawPoint(renderer, 0, 0);
// delete surface and texture
SDL_FreeSurface(fontSurface);
SDL_DestroyTexture(fontTexture); // have to draw a point before this
...
This then shows the two rects rendered before the text
If I set dstRect to NULL when calling SDL_RenderCopy then the text spans the whole window but I can see what was rendered before underneath the text.
Why am I having to draw a point after calling SDL_RenderCopy to stop what was rendered before from not showing up?
NOTE: Link to full source code https://pastebin.com/tRSFT0PV
This is a bug in SDL 2.0.10. It's fixed by https://hg.libsdl.org/SDL/rev/6ee12b88beed and this fix will ship with 2.0.11. Sorry about that!
I want to redraw only part of a GtkTextView widget. In the draw signal handler I tried many things for example:
GdkRectangle rect;
gdk_cairo_get_clip_rectangle(cr, &rect);
cairo_surface_t* surface = cairo_get_target(cr);
cairo_surface_t* newsurf = cairo_surface_create_similar(surface, cairo_surface_get_content(surface), rect.width - 50, rect.height);
cairo_push_group(cr);
cairo_set_source_surface(cr, newsurf, rect.x + 10, rect.y + 40);
cairo_fill_preserve(cr);
cairo_stroke(cr);
cairo_pop_group_to_source(cr);
cairo_paint(cr);
except that nothing really happens. How do I re-draw only a rect of the dirty clip region in cr or how (as I am trying) to modify cr so that the surface area has different dimensions?
To clarify further - I don't draw my own things. I want to set my own surface in the cairo_t passed in the draw callback of the GtkTextView for greater control of how the widget is rendered naturally. This new surface may be the same as the source surface in cr, but cropped or an earlier "snapshot" of the widget obtained with gtk_widget_draw()
I have a Gtk app written in C running on Ubuntu Linux.
I'm confused about some behavior I'm seeing with the pango_cairo_show_layout function: I get the exact "ink" (not "logical") pixel size of a pango layout and draw the layout using pango_cairo_show_layout on a GtkDrawingArea widget. Right before drawing the layout, I draw a rectangle that should perfectly encompass the text that I'm about to draw, but the text always shows up a little below the bottom edge of the rectangle.
Here is my full code:
// The drawing area widget's "expose-event" callback handler
gboolean OnTestWindowExposeEvent(GtkWidget *pWidget, GdkEventExpose *pEvent, gpointer data)
{
// Note that this window is 365 x 449 pixels
double dEntireWindowWidth = pEvent->area.width; // This is 365.0
double dEntireWindowHeight = pEvent->area.height; // This is 449.0
// Create a cairo context with which to draw
cairo_t *cr = gdk_cairo_create(pWidget->window);
// Draw a red background
cairo_set_source_rgb(cr, 1.0, 0.0, 0.0);
cairo_rectangle(cr, 0.0, 0.0, dEntireWindowWidth, dEntireWindowHeight);
cairo_fill(cr);
// Calculate the padding inside the window which defines the text rectangle
double dPadding = 0.05 * ((dEntireWindowWidth < dEntireWindowHeight) ? dEntireWindowWidth : dEntireWindowHeight);
dPadding = round(dPadding); // This is 18.0
// The size of the text box in which to draw text
double dTextBoxSizeW = dEntireWindowWidth - (2.0 * dPadding);
double dTextBoxSizeH = dEntireWindowHeight - (2.0 * dPadding);
dTextBoxSizeW = round(dTextBoxSizeW); // This is 329.0
dTextBoxSizeH = round(dTextBoxSizeH); // This is 413.0
// Draw a black rectangle that defines the area in which text may be drawn
cairo_set_line_width(cr, 1.0);
cairo_set_antialias(cr, CAIRO_ANTIALIAS_NONE);
cairo_set_source_rgb(cr, 0.0, 0.0, 0.0);
cairo_rectangle(cr, dPadding, dPadding, dTextBoxSizeW, dTextBoxSizeH);
cairo_stroke(cr);
// The text to draw
std::string szText("Erik");
// The font name to use
std::string szFontName("FreeSans");
// The font size to use
double dFontSize = 153.0;
// The font description string
char szFontDescription[64];
memset(&(szFontDescription[0]), 0, sizeof(szFontDescription));
snprintf(szFontDescription, sizeof(szFontDescription) - 1, "%s %.02f", szFontName.c_str(), dFontSize);
// Create a font description
PangoFontDescription *pFontDescription = pango_font_description_from_string(szFontDescription);
// Set up the font description
pango_font_description_set_weight(pFontDescription, PANGO_WEIGHT_NORMAL);
pango_font_description_set_style(pFontDescription, PANGO_STYLE_NORMAL);
pango_font_description_set_variant(pFontDescription, PANGO_VARIANT_NORMAL);
pango_font_description_set_stretch(pFontDescription, PANGO_STRETCH_NORMAL);
// Create a pango layout
PangoLayout *pLayout = gtk_widget_create_pango_layout(pWidget, szText.c_str());
// Set up the pango layout
pango_layout_set_alignment(pLayout, PANGO_ALIGN_LEFT);
pango_layout_set_width(pLayout, -1);
pango_layout_set_font_description(pLayout, pFontDescription);
pango_layout_set_auto_dir(pLayout, TRUE);
// Get the "ink" pixel size of the layout
PangoRectangle tRectangle;
pango_layout_get_pixel_extents(pLayout, &tRectangle, NULL);
double dRealTextSizeW = static_cast<double>(tRectangle.width);
double dRealTextSizeH = static_cast<double>(tRectangle.height);
// Calculate the top left corner coordinate at which to draw the text
double dTextLocX = dPadding + ((dTextBoxSizeW - dRealTextSizeW) / 2.0);
double dTextLocY = dPadding + ((dTextBoxSizeH - dRealTextSizeH) / 2.0);
// Draw a blue rectangle which should perfectly encompass the text we're about to draw
cairo_set_antialias(cr, CAIRO_ANTIALIAS_NONE);
cairo_set_source_rgb(cr, 0.0, 0.0, 1.0);
cairo_rectangle(cr, dTextLocX, dTextLocY, dRealTextSizeW, dRealTextSizeH);
cairo_stroke(cr);
// Set up the cairo context for drawing the text
cairo_set_source_rgb(cr, 1.0, 1.0, 1.0);
cairo_set_antialias(cr, CAIRO_ANTIALIAS_BEST);
// Move to the top left coordinate before drawing the text
cairo_move_to(cr, dTextLocX, dTextLocY);
// Draw the layout text
pango_cairo_show_layout(cr, pLayout);
// Clean up
cairo_destroy(cr);
g_object_unref(pLayout);
pango_font_description_free(pFontDescription);
return TRUE;
}
So, why is the text not being drawn exactly where I tell it to be drawn?
Thanks in advance for any help!
Look at the documentation for pango_layout_get_extents() (this is not mentioned in the docs for pango_layout_get_pixel_extents():
Note that both extents may have non-zero x and y. You may want to use
those to offset where you render the layout.
https://developer.gnome.org/pango/stable/pango-Layout-Objects.html#pango-layout-get-extents
This is because the position that you render the layout at is (as far as I remember) the position of the base line (so something logically related to the text) instead of the top-left corner of the layout (which would be some "arbitrary thing" not related to the actual text).
In the case of your code, I would suggest to add tRectangle.x to dTextLocX (or subtract? I'm not completely sure about the sign). The same should be done with the y coordinate.
TL;DR: Your PangoRectangle has a non-zero x/y position that you need to handle.
Edit: I am not completely sure, but I think Pango handles this just like cairo. For cairo, there is a nice description at http://cairographics.org/tutorial/#L1understandingtext. The reference point is the point you give to cairo. You want to look at the description of bearing.
I'm experiencing a frustrating issue trying to draw text using Pango and Cairo libraries in C in a Gtk application running on Ubuntu Linux.
I'm creating a Pango layout and then drawing it at a given location which is determined by the size of the text as reported by pango_layout_get_pixel_size, but the size returned by that function is wrong in both width and height, especially in height. Here is my full code:
// Create a cairo context with which to draw
// Note that we already have a GtkDrawingArea widget m_pGtkDrawingArea
cairo_t *cr = gdk_cairo_create(m_pGtkDrawingArea->window);
// Text to draw
std::string szText("NO DATA AVAILABLE");
// Create the layout
PangoLayout *pLayout = gtk_widget_create_pango_layout(m_pGtkDrawingArea, szText.c_str());
// Set layout properties
pango_layout_set_alignment(pLayout, PANGO_ALIGN_LEFT);
pango_layout_set_width(pLayout, -1);
// The family to use
std::string szFontFamily("FreeSans");
// The font size to use
double dFontSize = 36.0;
// Format the font description string
char szFontDescription[32];
memset(&(szFontDescription[0]), 0, sizeof(szFontDescription));
snprintf(szFontDescription, sizeof(szFontDescription) - 1, "%s %.1f", szFontFamily.c_str(), dFontSize);
// Get a new pango font description
PangoFontDescription *pFontDescription = pango_font_description_from_string(szFontDescription);
// Set up the pango font description
pango_font_description_set_weight(pFontDescription, PANGO_WEIGHT_NORMAL);
pango_font_description_set_style(pFontDescription, PANGO_STYLE_NORMAL);
pango_font_description_set_variant(pFontDescription, PANGO_VARIANT_NORMAL);
pango_font_description_set_stretch(pFontDescription, PANGO_STRETCH_NORMAL);
// Set this as the pango font description on the layout
pango_layout_set_font_description(pLayout, pFontDescription);
// Use auto direction
pango_layout_set_auto_dir(pLayout, TRUE);
// Get the pixel size of this text - this reports a size of 481x54 pixels
int iPixelWidth = 0, iPixelHeight = 0;
pango_layout_get_pixel_size(pLayout, &iPixelWidth, &iPixelHeight);
// Calculate the text location based on iPixelWidth and iPixelHeight
double dTextLocX = ...;
double dTextLocY = ...;
// Set up the cairo context for drawing the text
cairo_set_source_rgba(cr, 1.0, 1.0, 1.0, 1.0);
cairo_set_antialias(cr, CAIRO_ANTIALIAS_BEST);
// Move into place
cairo_move_to(cr, dTextLocX, dTextLocY);
// Draw the layout
pango_cairo_show_layout(cr, pLayout);
//
// pango_layout_get_pixel_size() reported a size of 481x54 pixels,
// but the actual size when drawn is 478x37 pixels!
//
//
// Clean up...
//
So, as described at the bottom of the above code, the pango_layout_get_pixel_size function reports a size of 481x54 pixels, but the size of the text on the screen is actually 478x37 pixels.
What am I doing wrong here? How can I get the actual correct pixel size?
Thanks in advance for your help!
The text you are displaying ("NO DATA AVAILABLE") is all-caps, and consequently has no descenders (letters which are partly below the baseline, like j, p and q.) Normally, when you measure the extent of a text box, you include room for the descenders whether or not they are present; otherwise, you will see odd artifacts such as inconsistent line separation depending on whether or not a given line has a descender.
Pango provides APIs which return both the logical extent (which includes the full height of the font) and the ink extent (which is the bounding box of the inked part of the image). I suspect you are looking for the ink extent.
I am trying to capture images from PDF and display them in my iPad application in a UIScrollView. App render the images to fullscreen (full size) when pdf page size is 1024 x 768 (standard 4:3 aspect ratio). But when the pdf page is of size 720 x 540 (same 4:3 aspect ratio but with less dimensions) I am seeing white border around the image. Below is the code snippet that i tried to capture the images.
CGPDFPageRef thePDFPageRef = CGPDFDocumentGetPage(pdfDocRef, pdfIterator);
CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB(); // RGB color space
CGBitmapInfo bmi = (kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedLast);
thumbnailWidth = 1024;
thumbnailHeight = 768;
CGContextRef context = CGBitmapContextCreate(NULL, thumbnailWidth, thumbnailHeight, 8, 0, rgb, bmi);
if (context != NULL) // Must have a valid custom CGBitmap context to draw into
{
CGRect thumbRect = CGRectMake(0.0f, 0.0f, thumbnailWidth, thumbnailHeight); // Target thumb rect
CGContextSetRGBFillColor(context, 1.0f, 1.0f, 1.0f, 1.0f);
CGContextFillRect(context, thumbRect); // White fill
CGContextConcatCTM(context, CGPDFPageGetDrawingTransform(thePDFPageRef, kCGPDFCropBox, thumbRect, 0, true)); // Fit rect
CGContextSetRenderingIntent(context, kCGRenderingIntentDefault);
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
CGContextDrawPDFPage(context, thePDFPageRef); // Render the PDF page into the custom CGBitmap context
imageRef = CGBitmapContextCreateImage(context); // Create CGImage from custom CGBitmap context
CGContextRelease(context); // Release custom CGBitmap context reference
}
CGColorSpaceRelease(rgb); // Release device RGB color space reference
CGPDFPageRelease(thePDFPageRef);
}
UIImage *image = [UIImage imageWithCGImage:imageRef scale:scale orientation:0];
How can I auto scale to full screen even when pdf page size is smaller?
I found the solution as below with scaling to rectangle.
(1) Get PDF page rectangle using
CGRect pageRect = CGPDFPageGetBoxRect(page, kCGPDFMediaBox);
(2) Do scale the rectangle and apply transform to Identity Matrix
CGAffineTransform trans = CGAffineTransformIdentity;
trans = CGAffineTransformTranslate(trans, 0, pageRect.size.height);
trans = CGAffineTransformScale(trans, 1.0, -1.0);
rect = CGRectApplyAffineTransform(rect, trans);
(3) Use kCGPDFMediaBox instead of kCGPDFCropBox to avoid cropping of pdfs when size is different than standard.